Low Refrigerant in Capillary Tube system 

 Not Enough Refrigerant


1. New AB lost some refrigerant 

2. New AB Leaks Refrigerant maybe inside Power Plate.

3. AB low on refrigerant and poor performance

4. New AB low on refrigerant  

5. Leaks Refrigerant General

6. Correction to misleading information

7. BD50 kit put together from Parts DIY Refrigerant Problems

8. Non Destructive testing analysis Low on Refrigerant

9. BD35 Performance Question Refrigerant Low on refrigerant

10. Adler Barbour Problems need recharge Low on Refrigerant

11. BD50 Refrigerant Charge For Adler Barbour with Power Plate

     Refrigerant Low

1. New AB lost some refrigerant 


Richard, I just purchased your 12 and 24 volt refrigeration manual and it is extremely helpful. The catalyst for buying the manual was to get better insight in case I need to recharge my Adler Barbour Cold Machine. When I was assembling it, the refrigerant was lost. Know that I have the book I can run some test to see if a charge is needed. If so, I need some additional clarification on how the connection is made to the low pressure side of the compressor. It currently has a cap, once the cap is undone, without the compressor turned on, will any refrigerant be loss?

 Answer: Before you do anything run the system for an hour and see if the evaporator has a thin layer of frost covering 100% of the evaporator. A properly serviced unit will form frost all over the evaporator with none outside the refrigerator on the return line towards compressor. If too much refrigerant was lost during assembly ¼ to ½ of evaporator will not have frost. I am assuming you do not have AB’s stainless Power Plate. Too much refrigerant destroys energy efficiency where a little less refrigerant can improve performance on some installations.

 Under the servicing cap is a needle valve like the one in your car’s tires. The reason for the cap is to hold the refrigerant in forever but these needle valves do leak a small amount in a few months and your system only contains 3 to 5 ounces of refrigerant.

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2. New AB Leaks  Refrigerant maybe inside Power Plate.

Last week I installed a new A/B Super Cold Machine with the Power Plate in a retro-fit ice box. I did a quick power up and was getting frost on the pressure side of the plate and thought that all I had left to do was to wire in the power, etc. I finally got the parts together and completed the wiring, mounted the thermostat, and was excited to make cold. Flipped on the breaker and the new BD50 hummed along.

I checked the evaporator from time to time and could hear a slight 'hiss' but no frost was forming. Oh-oh. After a few hours I finally gave up. It wasn't getting cold. The compressor was running constantly and could not be shut off with the thermostat (unless I unplugged it altogether).

My conclusion is I have a leak somewhere. I don't have gauges (yet) so can't measure anything. My question is whether or not I would have enough R134A left in the system to find the leak with soap/water mix. Secondly -- if I do have a leak and get it fixed at which point do I have to make the decision that the system needs to be evacuated prior to being charged? You talked about adding more to a system that was marginally charged. My guess is I would. Needless to say my first experience with piecing together my own system wasn't very good and somewhat depressing. Argh.

Answer:  It is important to determine whether this is your problem to correct or Adler Barbour’s. For many years the quality of these units has been excellent but I believe since WAECO got involved quality control and customer support have changed. An ounce of refrigerant (30 Grams) too much or too little before you received the unit can affect overall performance on pre-charged kits. Selling mix and match evaporators can increase the refrigerant charge error and there are cases where this happens.

 There are only two ways you could have caused this problem. 1. The initial insertion of the self piercing connectors were not lined up and more refrigerant was lost than normally expected. All of the connection O ring must be inside before sealing disc is ruptured. If this were the cause of refrigerant loss, then you would know by how long it took to push fitting in, and seating the O ring. 2. You failed to tighten the coupling tight enough to set the metal seal. The O ring is not the permanent seal as there is a metal to metal seal after the threaded nut is tightened. These Power Plates have been known to have leaks where line connects to plate. I would start the system and see if the line frosts at the same place it did the first time, if it does not then there is a leak and most of the refrigerant is lost. With no refrigerant pressure build up, the leak will be in one of the two units shipped to you or at the connections you made.

 If you believe you did not cause this problem because no leak occurred during assembly and the connections are tight I would call WAECO Adler Barbour and ask for them to replace the complete unit. If they refuse then ask the company you purchased it from for a replacement system. Remember warranty was built into the cost you paid. Responsible icebox conversion refrigeration companies do expect from time to time that they will have to replace these units. Unless you caused the problem it is best to get a warranty replacement I reported a case where the boater spent $2000 on one of these new systems from a different manufacturer because a test gas was shipped in one of the components. There were over six service calls and charges from different technicians.

 If you are unable to get this problem handled under their 100% warranty let me know. Here is what it will take to restore this system to a reliable new condition, so I would not want yours to be repaired if there is no refrigerant in the system now:

Add refrigerant and leak test.

If soldering is required, flow nitrogen through tubing to prevent formation of oxides in tubing

Repair leak

Replace filter/dryer

Leak test again

Vacuum air, gas and moisture from system

Service with correct amount of 134a refrigerant

Leak test again

 Reply: Thanks for your quick response. I am afraid that all has leaked out somewhere --I just need to figure out where. No frost formed (where it formed before) after 8 hours of running so something is amiss.
I called the factory this morning after following their troubleshooting guide. They asked me to do one test to check and make sure the compressor is, in fact, running -- that is to disconnect the fan. After that they will probably want to dispatch out a technician.
One quick question -- are these fittings 'one shot only' or are they designed to allow you to remove them and re-connect with minimal loss? No I didn't take them apart but am just curious about their operation. I know I got them good and tight following their instructions. At this point ifIwere to ask for replacement I would assume I would have to have all components replaced (evaporator, lines, compressor).

            Answer: The reason they wanted you to disconnect the fan is to eliminate its noise as it is very difficult to hear the compressor if the fan is running. Did they ask you whether the red troubleshooting LED was flashing? This would be important for them to know? If the LED does flash when compressor tries to run there is an electrical problem with fan or most likely your boat’s electrical system. If compressor does not run then it is not because some or all refrigerant was lost. If the LED does flash the compressor will not be running, you would not want a service man until LED flash sequence eliminates your boats electrical as causing the trouble.

 The disconnect couplings on your new system are not like the older disconnects once the disc inside is fractured all refrigerant will be lost if coupling is ever opened up again.

 Reply: I don't recall them asking first or whether or not I offered that there are no LED error codes whatsoever. I did verify the compressor operation by disconnecting the fan this evening. Compressor runs -- so I'll call them back in the morning. One thing I did note as I shut down everything on the boat other than the compressor -- that was I could hear the 'hissing' noise at the plate AND I heard a sound that one would describe as water dripping into a pan. Hmm... That to me doesn't sound like a good sign. I also noted and had a friend confirm, the plate appears to be bulging in the middle on both sides. The overall thickness is about 1" and our estimate is that, in the middle, there is an extra 3/8" overall.
Thanks for the help !!

Answer: You may have found out where the missing refrigerant went. The hissing sound is normal when liquid or gas is expanded leaving a restrictor orifice into a low pressure area. The dripping sound is not something I can understand. Most companies have had failures inside eutectic plates where evaporator coils leak refrigerant into eutectic material. Generally these eutectic plates (holding plates) use expansion valves and receivers to store extra refrigerant so when an internal evaporator coil failure occurs the stainless plate takes shape of a distorted ball. I have not seen a plate failure on a system using a capillary tube expansion device before but I would think that with such a small amount of refrigerant the plate would only expand. The only way to confirm this type failure is to pressure test system with 150 psi of nitrogen for 24 hours and staying clear of plate or add refrigerant and run system on 24 and off 24 hours. Once a failure occurs inside plate eutectic, material can inter refrigerant circuit, this means the complete system condensing unit, all tubing, and plate are scrap. If the plate is the problem there is no way I would replace only the plate.

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3. AB low on refrigerant and poor performance


First, let me thank you for your help. This website and your book have proved invaluable to all of us that own boats with refrigeration. Now this is the update on what has/is occurring. I purchased the A/B Super-Cold Machine. When initially installed, the box/evaporator had a temp of 18˚. The bottom of the refrigerator was 38˚ and the top was a little high at 50-52˚. Per your book I added a small fan with hose attached to circulate the air, with a result of the top now having a temp of 42˚. The thermostat that came with the unit has a 680 ohm resistor so the compressor is running at 3000 rpm. It is set at its upper limit to achieve these temps. The evaporator seems to have frosted over except for one corner in the back. This section is about 6 inches wide from the top to the bottom of the evaporator. Is this possibly a low freon problem or is it something more serious?
I would also like to add a speed control system and digital thermostat like you describe in your book. Would the Carel digital thermometer (I was going to use A/B's digital thermostat but it costs $320) and the Frigoboat SSC be appropriate for this box, or should I try something different? Do you have a wiring schematic for this design? The unit seems to be pulling about 4.7 amps when running.
Thanks for any and all your great advise.

Answer: It does sound like your refrigerator system is slightly low on refrigerant for a 13 cu. ft box. I hope you purchased the large 15 inch bin evaporator. With the thermostat set to full cold does the compressor cycle off and on more than twice per hour? How long is a compressor cycle from start to the next start? Do you have an amp-hr meter like the Link meter? Where do you plan to cruise in the future? Are you satisfied with the temperatures you are getting in the box now? What is your approximate location?

A 13 cu. ft. box with a BD50 compressor running at 3000 rpm, drawing only 4.7 amps and an area of the evaporator without frost does indicate a loss of refrigerant. Boaters who have installed Adler Barbour units have had this problem since Adler Barbour switched to the self piercing line connectors. There is an O ring in the connector that is designed to retain the pre-charged refrigerant while the self piercing disc is broken. When metal to metal contact is made between the male and female parts of the coupling the O ring becomes redundant. If special attention isn’t paid to the coupling alignment and follow up tightening of the coupling nut refrigerant can be lost.

Reply: Once it is determined that there is a small loss of refrigerant and it has effected the system’s performance what do you do? The unit is under warranty but I am told that Adler Barbour won’t cover loss of refrigerant at installation, because the line couplers were installed incorrectly. Now the real catch 22, these days where are you going to find someone knowledgeable in servicing one of these small capillary tube systems?
           Answer: After working with boats for many years and having a boat in salt water for over twenty years, I have found that mechanical equipment is more reliable than electronic equipment on a boat. As far as an electronic thermostat or an electronic thermometer they offer no better performance than mechanical units and their life expectancy is short. As to Frigoboat’s SSC control I don’t have a drawing of one connected to a Adler Barbour’s relay panel but I am sure Frigoboat will provide you one. Do you need the SSC?


Reply: Richard, the evaporator that we purchased is the VD-152...largest vertical evap that they sell. With the thermostat set to full cold, the compressor (monitored for 30 minutes) seems to cycle on and off every 5 to 6 minutes. For instance, at 0:00 on, 0:06 off, 0:10 on, 0:16 off, etc...I do not have an amp hr meter yet. Cruising grounds will be the tropics. I would prefer that it was a little colder but I can live with it at the moment. The boat is located in Cape Canaveral. I contacted A/B and they said they don't have anyone in this area who services their units. So I contacted West Marine where I purchased the unit and they gave me a repairman in the area to call. A/B then agreed to cover the cost of the service call when I told them I had contacted West.

I am assuming from your questions that the cycling on off every 5 minutes is not normal. Could it be the low refrigerant level? Will it do damage to the system?
And finally, when I get the system recharged on Friday should I consider installing the SSC?
thanks, Darrell

Answer: This quick cycling is not very efficient but it will not hurt the compressor.

Now the task is to lower the box temperature and maybe change the compressor duty cycle to 15 minutes ON and 15 minutes OFF at the lowest possible compressor speed to achieve the System’s Optimum Coefficient of Performance (SCOP). Nice words but what you really want is to have a good refrigerator consuming the least amount of amp-hrs per day.

The base line that you have recorded indicates that the capacity of the compressor is greater than the ability of the evaporator to absorb heat. This condition can be caused by:

· Low on refrigerant

· Thermostat aluminum capillary tube touching the evaporator somewhere along the evaporator. This tube, for correct thermostat calibration, must touch only in a single U shape under the plate designed for it.

·  Insufficient air movement over the evaporator.


Because the box is so large and the boat will operate in tropical climates, the compressor will need to run some days at mid day at 3500 rpm. Hopefully at slower more efficient speeds when the sun is off the boat.  A fixed or manual compressor speed change is not practical under these conditions as the box is too large. Your refrigerated box is twice the size that I recommend in my book to be refrigerated by a BD50 compressor in the tropics. When you are in really hot weather the compressor may need to run 24 hours a day at 3500 RPM.

Danfoss does offer an automatic speed control included in two of their modules along with a module fan that they require on BD50 Compressors which run at 3500 rpm.

Currently none of the boat refrigeration manufacturers offer the new Adaptive Energy Optimization (AEO) module. So the next best thing is to purchase Frigoboat’s SSC control and a two inch 12 volt fan from Radio Shack and installed it to cool the module’s heat sink.

Before you install the SSC controller and after refrigerant is added run the system full cold and check performance figures again including, Cycles, temps, and amps.

If the compressor still cycles too often and the box temps do not drop properly an additional fan in the box may be required.

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 4. New AB low on refrigerant  


Recently I installed a cold machine which I purchased about three years ago (BD50F w/large vert. evap.) When set at 4-5 for 12 hours, only part of the evap frosts over, and ice tray does not freeze when in contact with inside wall (as per instructions). I realize that this is likely due to inadequate 134a charge, but is it possible on a new install (i.e. could the tubing set have lost charged sitting in the box) or is it possible that the metal diaphragm piercing connectors leaked during the install. I have a manifold gauge set which I will hook up this weekend and check the low side pressure. Is there also a possibility that my condenser is partially blocked? (metal particles from the piercing valve if I over-torqued it?). If so will evacuating the system help?

Answer: This is the fourth time I have heard of this problem with Adler Barbour refrigeration units. The first one I was asked to check and service, AB paid the owner for my service call. I understand they no longer pay for servicing new units as they feel the installer caused the refrigerant to leak out when screwing the connections together.

Newer model connectors are of a design used for years in pre-charged air conditioning systems and I know of no problems from a broken diaphragm causing problems. When these connectors are connected by hand, an O ring first comes in contact and is intended to seal the refrigerant in until the tightening process is complete. The final wrench tightening will complete a metal to metal lifetime seal.

Yes there is a lot of other problem area you can dream up that could cause this but they are not indicated by the results you are seeing. Frost level is low indicating low refrigerant.

Things to remember before connecting gauges and servicing:

1. Purge refrigerant through gauge set to remove air and moisture.

2. Stop compressor before connecting gauges, as it may be running in a vacuum.

3. Everything in the system including the ice box needs to be 70˚ F. or above.

After the compressor is started the suction pressure will drop and stabilize this may take 10 minutes. Then warm the box, A setting of 6 to 8 psi would be the correct charge for 134a refrigerant. If at 10 to 20 minutes this pressure is low, add a small amount of refrigerant. Yes small amount, and then wait till it seeks a new stabilized pressure before adding more. If the system wad over charged, and yours is not, the pressure would be higher than 10 psi. The exception to these pressures would be if you have AB’s large 15 inch evaporator then the pressures should be 2 psi higher. A small overcharge of ½ ounce or more (15 Grams)of refrigerant will cause an increase of daily amp-hrs used.

If you are unable to adjust the refrigerant level in the first 20 minutes, stop and let the evaporator warm back up to 70˚F.  After 20 minutes, the suction pressure will automatically adjust down to lower temperatures and lower flows as the plate and box cools. Use pressures for servicing only in a time window between 10 and 20 minutes with a warm box. Fine tuning later is done by setting frost line (upper heat), confining it to evaporator.

After removing the gauge set be sure to replace the sealing cap with its seal still inside on the service fitting. Common slow refrigerant leaks are caused by poor sealing of these caps.

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5. Leaks Refrigerant General

Slow leak  Reported by Captain and helpful or unhelpful tips from others.


Sheesh! people. It's a Danfoss sealed compressor with one service port on the
suction side. With the system running the pressure on that side can range from
0 to 14 psi. With the system not running for awhile it will stabilize at one
pressure throughout. I never checked that pressure. I generally prefer to let professionals do most jobs that require specialized and expensive tools, not to mention expertise. A good workman is worth his hire, as they say.
However, the fridge manufacturer gives some simple tests that require no tools to tell you whether the system is under- or over-charged and, roughly, by how much. (Tinny gurgling sound? Hissing? Sounds of a mountain brook?) No gauge needed. Where on the evaporator does it stop frosting? How far out the supply
tube does the frosting go?

As for leak detection, no doubt an expensive gadget does the job better than
anything. But if Richard Kollman says a soap solution will detect very small
leaks, I believe Richard Kollman. At any rate, the system is doing just fine now. The beer is suitably cold and there is plenty of ice. I still think the problem was a blocked capillary tube
and not a massive leak.

Answer:  I will only reply once to this misleading game. Stay with the facts you have and forget the misleading information you read and hear from these hopefully well intended helpers. Your small refrigeration unit failed to cool enough to form frost over the complete evaporator after the system shut down for a long period. I believe I advised you that there are three likely areas where leaks are common on your unit. 1.  Line tube connectors, 2.servicing cap seal and 3. very small corrosion holes in the aluminum evaporator. Because your unit contains 85 to 120 grams of 134a refrigerant and from your description of frosted areas my guess was, refrigerant loss was 1 to 2 ounces. With this amount of loss and the time it took to leak out standard leak testing equipment might not find the leak. A competent technician might need to make more than one service call to confirm the leak using a two step Florissant dye and black light test.

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6. Correction to misleading information:

Capillary tubing mechanical clogging is very unlikely and maybe less than one in a thousand performance problems are caused by material blocking cap tube. When there is moisture freezing in cap tube, a plate temperature is maintained at 33˚due to freezing and thawing with no frost. If a cap tube is mechanically blocked, shaking it will not open the blocked area.

Your system when running should never see suction pressure over 10 psi and that is 10 minutes after start up with a 100 degree box temperature. Very few technicians have time enough and experience to service your unit in the field as accurately as you can.

 Hearing the hissing noise caused by refrigerant leaving cap tube is only an indication that there is refrigerant and oil being pumped and nothing more unless you have Superman’s ears.

After adding refrigerant your evaporator frosted properly but there is still a leak so your problem will return again.

DIY leak testing information I gave you before is done with compressor turned off. The secret in this process is to agitate the mixture on leak test area until the liquid surface tension against test area is achieved.

Mix up a small amount of dishwashing liquid soap and water 50/50 mixture to apply with a one inch paint brush. With 134a refrigerant bottle in upright position (Gas Only), compressor off, allow system pressure to increase to 30 to 50 psi and quickly feel with your hand for a leak. If there is a bad leak you can feel and hear it change as your fingers pass over it. If you did not find a leak add more gas until pressure stops rising. Now begin liquid foam tests.

Painting this mixture on a suspected leak area will not find a leak. Using the brush to agitate mixture into a shaving cream like mixture on a suspect area and sitting back watching the spot for a couple minutes will find the smallest leak if there is one.

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7. BD50 kit put together from Parts DIY Refrigerant Problems


I installed a BD50 w/AEO module, air-cooled condenser, large evaporator plate system (parts from RParts) about 6 months ago, in a 9cu.ft. icebox with 4in of blueboard insulation (also rebuilt). I pressure tested it before charging: it held 150lbs of pressure for 3 days without noticeable change.

As of three days ago it was staying cold just fine; three months ago I measured the duty cycle to be 20% (to maintain icebox temp ~36degreesF in an ambient 60degree environment, lightly filled with foodstuffs). I hadn't paid close attention since I measured the duty cycle, but I have a green LED next to the icebox to tell me the compressor is running, and the red fault LED also in eyesight. The compressor seemed to be running a normal amount for the past few weeks, and there was no action on the red LED.

The past two days I had the icebox turned off so I could install shelving for organization. I turned it back on last night and the compressor ran 12 straight hours to get the fridge down to temperature (from 60F to 38F)--there is not much food in the icebox either. Only 1/8th of the evaporator plate frosted over (and stayed that way for the duration of the 12 hours the compressor ran). It appears to be the first 1/8th of the tubing after the capillary tube.

Could I have damaged the evaporator plate during my construction project? Could this be a symptom of a damaged plate? Or perhaps I did not notice the condition before the past few days, and my recent project drew attention to it? If it weren't for the construction project, I would suspect insufficient refrigerant, caused by a slow leak somewhere, which I did not find during my installation. But wouldn't I have noticed that last week (before my project)? Would the green LED have been on all the time (it definitely wasn't running more than 50% of the time). Boy, I really REALLY hope I didn't damage the plate. I tried to be so extremely careful. I will be really depressed if that ends up being the problem. 

Answer: One area I like to remind people of is that if capillary tube system is serviced with a warm ambient temperature and then operated at a low ambient cooling medium performance will be degraded and frost area will be reduced. I do not believe that reduction of 80% frost area in this case is causing your problem.

A very slow leak in low pressure side of system would have been detected 6 months ago with the three day test. The question now is the loss of refrigerant did a micro leak develop over time or was it a new leak due to a very small hole caused by working on the box’s interior.

Sometimes leaks are caused by not using special refrigerant flare nuts. Light weight hardware store nuts tend to expend at a different rate as temperature changes causing leaks. Many times failure to use servicing fitting caps with a seal inside can cause small leaks. If refrigerant loss was slow over time when in operation evaporator frost coverage would slowly be reduced beginning with a small area. I have seen a frosted area reduced to 50% in six weeks and when system is off a few days all refrigerant is lost. When system is not running the low pressure side of system is the same as high side.

If the evaporator prior to the three day shelf work, had frost covering 90% of its surface and now is only 20% I would suspect you damaged the evaporator plate.

The only recommendation I can give you is to add refrigerant in small amounts till frost covers 80 to 90% of evaporator. Then stop compressor and test for leaks at all connections with a mixture of 50/50 liquid soap and water. It is important to use a one inch paint brush against test area forcing mixture into a shaving cream texture. This method of leak testing is slow, one fitting at a time, but it will find leaks as small as ½ an ounce a year. Leaks in aluminum evaporators are very hard to find and are not repairable. If you drilled any new mounting holes in evaporator I would check them first. Again pressure in low side of system when unit is running will be less than 8 psi so leak testing is best done with warm box and system turned off


Reply: WOW am I glad you exist on the internet, thank you so much for the advice. That is great to know, that leaks in the low pressure side can be masked until the system is shut down entirely--makes complete sense but I had never thought of it.
Is it possible that there is nothing wrong at all? I charged the system when it was about 70˚ ambient; now it is about 45˚ambient. Could that alone account for the reduction in frost pattern from 100% to 20%? You may have been saying not, when you wrote "I do not believe that reduction of 80% frost area in this case is causing your problem" but I am confused about what you meant by that statement.
So I will charge the system with UV dye refrigerant and then look for leaks.

Answer: If it loses its charge rapidly, then you will have strong evidence that a hole in the evaporator plate is the culprit. Additionally, if the leak is that large, you should be able to see the UV dye with the blacklight. If after two days it is still running strong, with no evident signs of leaks with the blacklight, then you have good evidence that the leak was a long slow one, and you will need to test each fitting with the soap/water mixture.


Reply: I have your book; it convinced me of the futility of attempting to repair any holes in the evap. plate, so if that is the culprit I will replace it.

If there is a slow leak, over time it draws in moisture that contaminates the system, correct? So it can probably be recharged a few times, but in the end moisture will be sucked in through the hole in the low side and clog the capillary tube, at which point a full "reboot" (leak repair, vaccumed to remove moisture, filter/drier replaced) will need to happen anyway, right? Any sense of how long it takes for the moisture to contaminate the system through a slow leak?

Additional data & responses to your comments: 1 When I first built the system I DID have a slow leak (this was determined because it did not hold the 150psi for a few days, it lost a little bit). I tightened up the two flare fittings joining the tubing run to the refrigeration fittings at the compressor, then retested and it held the pressure. If there is a micro-leak in the system, I would speculate that one of these flare fittings would be the culprit, probably the flare fitting on the low pressure side from what you wrote. You said that the pressure test should have identified this leak, though, so I will keep it as a suspect hypothesis.

2) Unfortunately, and to my immense annoyance, I cannot recall what the duty cycle or frost pattern was prior to messing around in the icebox two days ago. I know that it wasn't 100% duty cycle just from vaguely paying attention to the compressor running, but I have no information beyond that. I rack my memory for clues, without success.

3) I used all refrigeration flare fittings from RParts in the system construction (it was their 1M kit).

4) I used a gauge set with good o-ring seals to originally charge it.


Answer: Refrigerant charge on a system using a capillary tube flow control device must be correct or performance will be degraded. As the condenser’s cooling medium, in your case air, changes temperature the pressure and temperature of refrigerant leaving condenser will upset the equilibrium of the liquid and vapor passing through the capillary tube. Factory charged refrigerators are generally charged with a fixed volume of refrigerant by weight based on standard day cooling medium temperatures. When these small cap tube systems are field serviced on a boat in the north to correct evaporator superheat and then transit south to the tropics evaporator super heat will be low causing frost to extend beyond evaporator. In you case going from warm to cold condenser cooling medium would reduce the frost area on the evaporator. I do not believe that initial low refrigerant is the only cause of your problem, so add refrigerant and leak test.

Florissant dye and a black light is the best way to locate leak areas. To enhance the dye. I also use special glasses. For these small units I recommend 10 to 20 drops of dye. The 4 ounce cans of refrigerant and UV dye contain ¼ ounce of dye and a mixture of oil and refrigerant and are intended for systems containing 2 to 5 pounds of refrigerant, this may be too much oil and dye for your system. I warn about too much dye because car manufactures say too much dye in their systems cause compressor problems. Do not mistake the regular non UV dye cans also sold to detect leaks. It is a good idea to test areas first before adding dye as there are materials that under black light will glow the same as dye. The material tie wraps are made of will glow. After finding a leak area with dye, I follow up with the soap test to further pinpoint leak. The best results with black light will be in a dark boat.

Reply: One more thing--perhaps I am overlooking an obvious answer, but how does one add just a few drops of UV dye to an already charged system?

Answer: To insert dye you must solve two problems first: Find some of the Florissant dye and acquire a ¼ to ¼ flare brass union to screw into end of blue servicing hose so that dye can enter hose. Do not add more than 20 drops of dye.

Dye can be added to the blue hose of the servicing gauge set. Begin with both red and blue gauge valves closed. Connect refrigerant bottle to yellow hose. With blue hose held vertical open blue valve and purge refrigerant through gauge set out through blue hose, then close blue valve. Refrigerant is heavier than air so keep blue hose vertical while adding dye. Connect blue hose to low pressure side of compressor. Turn refrigerant bottle upside down so that liquid refrigerant will flush dye into system. Open blue valve for 5 seconds then close valve and turn refrigerant bottle with gas only side up. Wait several minutes before starting compressor so that liquid refrigerant will have returned to gas in compressor. Service with refrigerant adding small amounts and then wait till low pressure stabilizes before adding more. Run system a few days to mix dye with oil. If evaporator stays covered with frost then turn compressor off for three days. When frost line on evaporator no longer covers 90% of evaporator, use black light to find leak.


Reply: Should I add any oil while I'm doing this? I now have a small container of the UV dye (in a plastic bottle with screw-top cap, unpressurized).
-I have the yellow glasses and a small penlight (really very cool to look at everything with that setup, I have to say). I have a 1/4-1/4 flare brass union.

To confirm: So I put the flare union on the end of the blue hose (the end that attaches to the service fitting), hold it vertical in my hand, and purge it. I continue to hold it vertical to prevent air from entering, and then I add 15 drops of the UV dye into the flare union, letting it drain down into the hose. Then I remove the flare union, and gently move the end of the blue service hose down to screw it onto the service fitting--this would be when I am most worried about air slipping into the system, as I am moving the hose and screwing it onto the horizontal service fitting. I leave the service fitting closed to the gauge set while doing this.

Then I hold the refrigerant can above the level of the gauge set, and invert it. (blue valve closed). Liquid refrigerant piles up against the blue valve, then I open the blue valve for five seconds and then close it. Liquid refrigerant piles up against the service fitting, then I open the service fitting and the liquid refrigerant enters the system, flushing the dye out of the hose and into the system with it. Then I wait a few minutes for all the liquid refrigerant to boil off in the system (thereby avoiding liquid slugging of the compressor).

Then I start the compressor and service with additional refrigerant as necessary to obtain a 100% frost pattern on the evaporator.

Then I put everything away and wait until it is apparent that some refrigerant must be leaking away, however many days or weeks that may take, and it will be evidenced by a diminished frost pattern on the evaporator.

Then I take out my glasses and blacklight and go searching.

Did I get all that right? And the minute amount of air that slips into the hose as I'm screwing it onto the service fitting is acceptable, I'm supposing, since this is how you're saying it is supposed to be done. This is pretty cool stuff. And I'm pretty excited that I'm learning how to do it all myself.

Answer: You are on the right track. When adding liquid refrigerant the bottle does not need to be higher than gauge set just upside down.

After removing ¼ union I put my finger over end of hose until connection to unit is made. You may want to use a syringe needle to add dye to hose as gas bubbles will be coming out as oil goes in.

Once hose is connected open three way suction servicing valve halfway then open blue gauge valve for five seconds. With both valves open at the same time liquid will flow into unit taking dye with it.

Reply: Ok, I hooked up the gauge set to check the operating pressures, before doing anything else, and when I saw that the suction side was pulling somewhat of a vacuum, I decided to modify the plan.

I was thinking that there was potential for air (maybe moisture) to have entered the system if the leak was on the suction side. Also, when I went to the refrigeration supply, they were having a sale on a vacuum pump, so I bought it. Then I borrowed a guy's micron vacuum gauge from down the dock, and vacuumed down to 450 microns, and closed off the system. Within 20 minutes it had risen to 520 microns, confirming a leak. So I let the system equalize with ambient pressure, then added 15 drops of UV dye to the gauge, set the suction side hose into the end with the male-male flare union as you described. Then I vacuumed down the system to 450 microns and charged with refrigerant. Now I am waiting for leak to present itself.

I have doubts that the amount of UV dye will be successful in identifying the leak: I overcharged very slightly at first, and bled off a tiny amount of refrigerant from the connection at the flare fitting. Only then did I realize my mistake: I probably released UV dye onto the area, reducing my ability to identify the leak. So I put on the glasses and looked around with the light and couldn't see anything at all. This causes me to doubt the effectiveness of it showing a leak. Though perhaps, after it runs for a few days, the dye will have mixed better with the refrigerant.

The dye seems to dry/stick to surfaces, though, so perhaps most of the dye ended up painting the inside of the blue hose on my gauge set, and very little made it into the system. I don't know, and for now I'm not going to stress out about it. We depart for Mexico in two weeks, and for now my icebox is cold and my food is unspoiled. I have a vacuum pump, a couple of extra filter/driers, and a greatly improved understanding of my problem, so I'm confident that I can deal with whatever wherever, even down in Mexico or the South Pacific this summer (fingers crossed!) if I have to. If the dye doesn't show the leak, I'll test each fitting with the soap/water method, which I now understand was probably the most thorough approach to have taken in the first place (which I should have known from your book and advice, but was naively looking for a shortcut).

Thank you very much for your excellent advice and patient explanations. Your book has been very helpful to me in gaining an intuition about the various specialized problems that may arise in our small boat systems, and the corresponding approaches to fixing said problems. Above and beyond the book, this forum and your responses to my questions have tripled my refrigeration knowledge (albeit not very large to begin with!), and it brings me happiness to be able to learn and understand how to take care of these things for myself. You have my gratitude!

Answer: A 30 micron change in 20 minutes I would believe is normal as trapped liquid moisture is being phase changed to gas. When 12,000 microns of vacuum is equal to one inch of vacuum gauge indicated vacuum a 30 micron change does not prove there is a leak. If system was vacuumed for four hours with system’s ambient temperature of at least 100˚F and vacuum reduced to 5,000 microns in 20 minutes then somewhere something is leaking and it may even be the servicing gauge set or its hoses.

Ten drops of dye is sufficient for your system. The leak you have, if there is one, is a micro size leak and will not display visible dye for many days with system running or when frost area coverage of evaporator is reduced by 50%.

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8. Non Destructive testing analysis Low on Refrigerant


I am about to re-gas my system with 134A, but…. How do you know how much gas to put in? Everything still works, BUT I think it should be colder. I don't have pressure gauges (yet) so I will confirm what is happening on that side of things soon. I also need to check the temp in the cool box. To prove I've done my homework the answer to my question was high pressure 110 psi. and low pressure range between 5 and 10 psi, however, let everything run for at least 10 mins to settle down.

Answer: Experience proves a boat captain needs to be smarter at analysis of refrigerator problems than a so called refrigerator service technician because no two systems have the same problems. Your suggested approach to locating a problem is a-round about service tech’s approach to be able to charge customer more money. The decision that refrigerant needs re-gas or connecting gauges is premature and may guide you in the wrong direction wasted hours of system down tine while doing destructive testing.

In this case you know cooling performance inside box is not what it should be. Looking for unusual temperatures throughout refrigerant cycle by non destructive ways may be all that is needed to pinpoint the problem. Compressor compresses refrigerant vapor and high pressure gas gets warm due to compression and sent to condenser where most of heat is removed. Gas when leaving condenser is cool to a warm high pressure liquid and filtered on its way to refrigerant flow control device, in this case a long orifice capillary tube, the only major restriction to refrigerant flow in this complete system. After flowing through capillary tube high pressure and now high velocity liquid is sprayed into low pressure areas of evaporator where it absorbs heat as it makes a phase change of liquid to a gas. The reason refrigerant liquid must make this phase change only in evaporator is so box cooling process occurs inside evaporator and not somewhere else in system. Gas return line form evaporator to compressor may be cool but not frosted.

Frost anywhere in the refrigeration loop other than at the evaporator will indicate too much refrigerant or a restriction to flow on this cap tube system.  Too much refrigerant would be from someone tampering with refrigerant. There are areas where there are slight restrictions that can collect material reducing flow thus causing a cold or frosted spot such as filter/dryer, or solder joints and refrigerant line connectors.

Picture attached to your post shows a large amount of frost on what appears to be suction line connector. If this is suction line and line between it and the evaporator is not frosted, there is partial blockage inside this connector. If the line all the way to the evaporator is frosted and there is no frost on the evaporator,  flow restriction is where frost starts.

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9. BD35 Performance Question Refrigerant Low on refrigerant


Last year with your book as a reference and your answers to help, I installed a new quick connect to both my A-B compressors- both BD3 with R134a, and recharged to a 5.5A current draw after 20 minutes with pure R134a.

I never ran the freezer very much last year after recharging so I don't have good performance data on that unit, but the refrigerator ran much better with adequate cooling and reasonable power consumption.

This spring, the initial current draw was in the 4-4.5A range on both the refrigerator and freezer compressors. Frosting of the cold plate seemed to take a long while also.

Reviewing my data that I recorded last year at recharge, it appeared that the low initial current and up to 20 minutes was likely due to a slight R134a loss.

I then added a very small amount of R134a to both the refrigerator and freezer compressors being careful to purge the charging hose each time. I added small spurts until the current draw at 20 minutes was between 5-5.5A.

Now I am on a four week cruise and the power draw of these two units seems excessive. Overnight I measure the power draw to be about 60AH for 8 hours. The refrigerator temp is holding about 35F and the freezer temp is between 11-19F.

I think the refrigerator is running fine, but the freezer is my concern. It seems to run for long periods even when the temp is at 11˚F. The current draw at 11˚F is 5.2A. The thermostat setting is at 4. The inlet connection and inlet line (about 20") are all frosted within the box. The connection to the return suction line is frosted all the time, and occasionally I have observed the return line (about 20") also being frosted within the box.

Question: Do these conditions indicate too much freon? Overall the total power consumption is about 175AH per day. This seems excessive to me as I believe that the refrigerator should be about 60AH. I would expect that the freezer would draw more but how much more? The refrigerator is about 7.25 cu ft and the freezer is 3.5 cu ft with 3" walls. Last night I turned the thermostat to zero and the freezer shut off. I then put it back to 3.5 and left it overnight.

This morning the freezer had warmed to 24˚F from 11˚F last night (over 9 hours) and the freezer compressor wasn't running. I tapped the thermostat and a few minutes later the freezer compressor began to run. Is it possible that the thermostat is "sticky" and is just causing the freezer to run excessively? I am not familiar with thermostat failure modes.

Answer: As long as Danfoss BD compressor runs and there is cooling you should not adjust refrigerant volume based on amperage. Tampering with refrigerant is destructive testing in most cases. Your unit has a capillary tube expansion device so correct refrigerant volume is always determined by temperature of ambient air cooling medium passing through condenser and frost area coverage on evaporator. In cool weather there will be slightly less evaporator surface area frosted and in hot weather there will be slightly more cooling of line outside of refrigerator. When you have a thin plate evaporator with correct refrigerant charge and proper condenser cooling the evaporator’s frosted area will be 90% to 100% covered and no frost on return line outside of refrigerated area. Too much refrigerant wastes energy because the compressor cycles too often and the cooling effort is not all in the evaporator where it should be.

On this unit the thermostat is a switch controlling the evaporator’s temperature. Its calibration depends on where and how its sense tube is contacting the evaporator. When correctly installed, thermostat will produce an evaporator temperature of about +12˚ F with control knob set between 3 and 4.  Box temperature will be relative to box design and present heat load.

It is possible for thermostat to freeze up and keep compressor running continuously if it is mounted too close to evaporator plate. Spray inside of thermostat switch with WD40 and work knob through off position several times. If problem reoccurs replace it.


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10. Adler Barbour Problems need recharge Low on Refrigerant

 Problems:  Re charge system. I am using a small car style 134a refrigerant.
 I need to know how much to install in the system. That is: pressure’s on the
 low side. Do I use a temp chart at 75˚F ambient and what pressures should I be reading Can    I tell by reading the temp on the line sets?
 Attempts to correct problem = I charged the unit I think I over charged it
 Thanks for your help
Answer:  am assuming, if you are adding 134a refrigerant, that your compressor is either a
BD3 or BD50 and not a BD2.5.  Turn compressor off first. Purge air from
hoses then connect refrigerant hose to suction port. With bottle upright, to
add gas not liquid, allow only 2 ounces of refrigerant to enter system, then
shut off bottle and start compressor. The quickest way to charge system
correctly is to use an ammeter in power wire and very very very slowly add
refrigerant until amperage reaches 5 amps. As evaporator cools amperage
will be less than 5 but never above 5.5 amps. Then from this point on ignore
amperage and run unit for 2 hours checking frost on surface area of
evaporator. Your unit will be charged correctly when the evaporator’s surface
area has frost covering 90 to 100% of its surface and no frost on return
line toward compressor. If frost area is less than 90% add refrigerant. Your
unit will hold from 3 to 5 ounces of refrigerant. With 1/2 ounce too much
refrigerant system will deliver poor performance. If you do not have my
12/24 volt refrigeration manual see if one of the other boaters has one you
can use. The above method of adding refrigerant will not harm your unit and
  the box will get cold.

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11. BD50 Refrigerant Charge For Adler Barbour with Power Plate

Refrigerant Low


Three amps while running is confirmation that some refrigerant has been lost.

Once you have confirmed that you have lost refrigerant, you will need to carefully follow the steps below to solve the problem.

First leak test: Leak testing should be done by using a 50/50 mixture of liquid soap and water. To enhance this mixture and break down the liquid to increase surface tension a 1 inch paint brush is used to stab suspect area creating shaving cream type foam. A slow leak may take a minute or two to show up. I know that this is tedious but it will save you much time and aggravation in the future if it is done correctly.

Another important step will be to purge moist air out of gauge set before connecting it to compressor.

AB’s power plates now, I believe, have O ring fittings so if a leak is found they will need to be replaced.

Leak testing of power plate connection must be done with a warm plate and compressor off. With compressor running pressure on these fittings will always be less than 10 psi.


These are the leak testing steps to follow:

•Compressor is off.

•Before using gauges make sure blue gauge reads 0. If not make a note of error.

•Connect 134a container to yellow hose of gauge set. Both valves on gauge set will be closed. Any container of 134a is OK unless this container also has an oil charge. You do not want to add additional oil.

•Do whatever you need to do to pressurize yellow hose.

•Remove leak protector cover from refrigerant service port coming out of compressor dome.

•Make sure that the blue hose is connected correctly to gauge the end with valve core depressor will be at compressor end but do not connect.

•Now purge yellow and blue hoses by opening blue low pressure gauge valve for 3 seconds close valve and NOW connect blue hose to compressor dome service fitting. Red hose will not be used.

•With refrigerant bottle upright open blue valve letting gas refrigerant into system until pressure stops increasing on blue gauge and close blue valve. The pressure in plate will be relative to plate temperature this is why a warm plate is best for leak testing. A 70 plate with 134a refrigerant will produce around 70 psi on blue gauge.

•Now begin leak testing with above method defined as it will locate ½ ounce leakage per year if done properly.

Final steps to follow when servicing with refrigerant


•Because I don’t know what resistor is in thermostat wiring I am assuming your compressor is set to run at 3000 rpm so lets use a base amperage of 6 amps under the following conditions, power plate 70 to 80˚F  before compressor startup

•At 10 minutes after compressor startup refrigerant volume must be adjusted very slowly to 8 to 10 psi on low pressure (Blue) gauge, at 20 minutes pressure should begin to drop as plate cools so do not add more refrigerant based on pressure. If refrigerant is added too fast, the compressor will shut down on overload.

•After 20 minutes with 70 to 85˚ F  ambient air temp in boat and no frost on power plate amperage should be near 6 amps if not add small amount of refrigerant.

•As plate develops frost cover and continues to get colder suction pressure will continue to drop. As suction pressure drops so will amperage.

•When connecting or removing hose connection compressor must not running this prevent air from contaminating refrigerant.

•When servicing is complete be sure to replace leak proof cap making sure its rubber seal is still inside.

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