LED Trouble Flash Code Tech Tip #2

Do not trust the Danfoss BD 35 and BD 50 compressor Troubleshooting LED or a service technician when they say your BD compressor has failed. Experience shows that troubleshooting LED code signals are not always reliable and service techs are almost always wrong about BD compressor failures. Here are some examples representing many reports:


  • Because the micro processor inside the Danfoss, variable, speed compressor’s electrical control module only has room for one trouble report at a time, a follow up second problem can cover up a previously stored problem. When a compressor is running and power is interrupted ,causing a low voltage spike, an automatic restart will occur causing the module to terminate the start and it will send a low voltage LED single flash every four seconds. If the compressor attempts to restart automatically by module before the refrigerant pressure is reduced, an overload may occur causing the module to now send a three LED signal, which masks the low voltage signal. The only way to determine if the fist signal was not covered up is to turn off the power to the unit and wait three minutes for pressure to equalize before turning the unit back on while you watch for the first LED code signal.
  • Danfoss and system assemblers tell us 3 and 4 flashed error codes of LED indicates compressor problems with the Rotor Blocked mechanically or Refrigerant pressure too high. After testing many variable speed BD modules ,I now know that there are failures inside a control module that will trigger the 3 flash error codes even though the refrigerant charge and compressor are fine. Resent problems prove that poor ground wires have triggered three flash error codes. The most common cause of Danfoss BD compressor three flash error codes are excessive refrigerant charges and contaminated gas vapors, such as air or test nitrogen which were not properly evacuated at the company assembling kits. Also Internet reports show most three LED codes occur after a service technician adds too much refrigerant.
  • A 5 flash error code is supposed to be a Thermo cut-out of the electronic control module. to Correct replace module. Danfoss warns about module cooling and requires an extra fan on the module if the compressor is ever to be operated at max speed. I believe fan cooling is important on all water cooled units to prevent module failures.
  • See, Tech Tip #1 conditions on Adler Barbour’s add on circuit board which caused false three flash LED codes when the  compressor and module were not the problem.

There are troubleshooting items about refrigeration that most repair people don’t know about your Adler Barbour, Frigoboat, SeaFrost or other type of 12/24 volt refrigeration units. The following points mainly applied to Danfoss BD variable speed compressors installed after 1995.

Troubleshooting the newer after 1995, Danfoss variable speed BD compressors when they are equipped with troubleshooting LED is easier if the following information is understood:

· LED will not signal if there is no power to Danfoss Control module.

· LED will not signal if thermostat circuit is open.

· LED will not signal if compressor is running continuously with poor or no cooling.

· LED will not signal if system is low on refrigerant, the compressor will run with little or no refrigerant and still show no LED signal.

· LED will flash 3 times every 4 seconds if there is way too much refrigerant in system.

· On Adler Barbour CU100 and CU200 LED will not flash when the compressor stops due to a problem inside the add on stainless box. This seems to be caused by poor solder connections to the fuse holder or a damaged circuit board inside the stainless box.

· If no one has tampered with the refrigerant and the refrigerant flow is blocked, the compressor will not stop nor will the LED flash, on this type system. This is a common problem on Frigoboat keel cooler systems. If refrigerant is added it will only cause additional problems.

· If there is too much refrigerant or contaminated refrigerant, the compressor will not start and signal with three LED flashes.

· Unlike automobile computers Danfoss electronic module's micro chip only has space for one memory. Because only one memory is all that can be stored, it is possible for a second problem to mask over the signal covering up the first LED signal. Say, the first signal is due to a low voltage and gives a one LED flash every 4 seconds, the compressor will stop and try to restart in 20 to 40 seconds. If the refrigerant pressure has not equalized in this short off cycle, a restart attempt can cause a three LED flash signal indicating an overload. When a three LED flash is indicated, always confirm it by turning the refrigerator power off. Then while watching the LED turn the power back on. The first signal code you see is where the problem is located.


If you still need help before calling a service technician, Email me your questions. These Tech Tips are my way of keeping my books revised with current upgrades.