Danfoss BD35F 5 blink led flash issue

[Matt Johnson]

As the title said, I'm getting a 5 blink LED diagnostic flash on my Danfoss compressor. The Grunert manual say this is attributed to overheating and the refrigeration system is overloaded/ ambient temp is too high. Now we are in Guatemala, but for once, the temperature is actually pretty nice and cool.

The compressor feels cool and everything else seems the same cool temp (no obvious overheating). Ventilation in this area shouldn't be an issue, and no other led codes are flashing when the unit restarts after being turned off. I disconnected the ecu and reinstalled, but it instantly starts the flashing the same 5 blinks again.

I googled Danfoss overheating and other search strings, but all I can find is info on 1-4 codes and mention of 5 flashes.

Any ideas? We were just about to head out for Belize, but not without refrigeration!

[Richard Kollmann]

I know this may be a strange suggestion but try running a new temporary ground wire from module to battery ground.

I am assuming the metal heat sink on module is not warm. It is my understanding that when circuitry inside module reaches 130 degrees a safety circuit will stop compressor and produce a five flash LED code. If compressor is running at high RPM and heat sink is hot Danfoss recommends a small fan is needed to cool module.

I suppose there could be too much resistance in thermostat circuit causing compressor to over speed. Try disconnecting wires from module thermostat terminals C and T. Then place a jumper across C and T terminals, This will try to run compressor at its lowest speed of 2000 rpm.

If these suggestions do not help you need to try another control module.

Please advise solution when refrigerator is up and running again as five flashes is very unusual. When working with an Adler Barbour after testing module a 4 LED code turned out to be a bad ground.

[Matt Johnson]

Richard,

Great to hear from you, but surprised you're working on the weekend...it's hard being the expert in your field isn't it?

The heatsink was not hot at all, but I don't know how long the unit had by in safety mode before I found it. It may cooled by then.

I installed a new ecu and it fixed the immediate issue, but I'm worried it will come again. If the circuit overheated on my module, will it reset itself after awhile, or is this one dead now?

I'll try reinstalling the bad (5 blink one) and run the test you gave, but a new module is working fine without the dreaded blinks

This is the second module I replaced in this unit this year. The first had a three blinking issue that turned out to be thermostat related. Unfortunately, I had already swapped out for a new ecu by the time I found the thermostat problem. I guess I may still have the thermostat issue after all.

[Richard Kollmann]

Johnson, I have been providing free technical services to remote locations for over 60 years. The first 34 years communication was by mail and phone now I only answer E Mail. At 80 I can no longer handle 3 AM calls from Japan.

To better understand Danfoss LED codes go to my web site and find TECH TIP #2.

Yes there is a reason why your module failed.
Short Module Serviceable Life can be caused by how refrigerator was installed.

Danfoss has always experienced problems with electronic control modules on BD compressors. After ten to fifteen different Danfoss module models still randomly failures occur with no warning. If we exclude lightening strikes and corrosion due to water module failures seem to be caused by voltage spikes or heat.

Voltage spikes at module are not always visible with a meter and can be present on any boat. Unstable voltage is why the module must receive power direct from battery buss using correct size wiring, fuses, circuit breaker and switches that allow no voltage drop. When compressor is correctly wired to battery buss battery will absorb voltage surges like a very large electrical capacitor reducing module electronics failures. When refrigerator is powered from a branch circuit breaker panel any item in that panel can cause a damaging voltage spike when that item is powered up or powered down. Any relay when power is turned off sends a voltage spike back towards the source. Windless, power wench, generator start relays and even cabin light relays can damage refrigerator control modules if refrigerator is wired through a circuit breaker panel instead of main buss.

Module overheating maybe the primary reason for so many electronic control module failures. Through the years Danfoss has designed static air heat sinks on modules to conduct and radiate heat away from transistors and other components inside module. Module heat increases as compressor load (amperage) increases. Danfoss’s installation application data sheets have always assumed system designers and installers would insure compressor design power amperage limits were not exceeded. What you will find in the marine industry is the elimination of module and compressor cooling air along with higher than design compressor heat loads. Only Danfoss’s AEO modules have built in module cooling fans. Danfoss’s variable speed specifications for BD50 require an additional fan for cooling control module if compressor is to be operated at maximum capacity (3500 rpm). All of the following conditions can cause module overheat failures; High condenser cooling temperatures, Repeated attempts to start do to an overloaded compressor, First box temperature pull down in a hot climate, System ambient temperatures above 105 degrees F, and too large or poorly designed holding plate evaporator coils. Failure to maintain good cool flow of condenser air, a normal maintenance item, should not be overlooked as cause of module failure.

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