Troubleshooting Danfoss BD35 / 101N0210 unit where compressor fails to start

[SailorMcCruise]

Hello all,

I have been using an ice-box-converted-into-fridge system which I inherited when I bought ye olde boat i have been splashing around with.

It is based around a Danfoss BD35 compressor and a 101N0210 electronics unit.
I had posted here a while back, since the system wouldnt cool properly but it seems that this issue had been fixed after a knowledgeable fridge-repair-person did exchange the coolant and repressurized the system a few months back.

Now unfortunately the compressor stopped compressing and my champagne, my caviar and all the other unseen riches from the fridge's depths are just a shadow of their former self.

I have eagerly followed most of the relevant troubleshooting tips I have found here and would like to share the results, so I can maybe get the system running again.

Symptoms /measurements ( with bridged thermostat ):
When the system wants to start, the fan begins running and the compressor jolts once as if trying to start. The led I installed flashes three times.
The voltage going into the unit is 13.3 V, at the ( running ) fan I measure 11.7V
The voltage at the compressor cables is around 34V when starting and then drops slowly to a steady 13.3V.
After disconnecting the compressor cable I did not detect a short between one of the leads and the housing. The resistance of between the leads is around 3.5Ω

The system starts, runs for a while without the compressor, just the fan, the stops and starts again.

The compressor has some corrosion on the outside ( mine is a wet boat ) but I have no idea if the inside would look the same. see image.

If I can find a similar system I would probably try to see if my electronics unit would work with a different compressor first, to continue troubleshooting.

Thanks for all hints, ideas and suggestions.

[Coolerking]

Try disconnecting the fan and see if the compressor runs.

[bensolomon]

Bypass the thermostat inside the ice box. If you take the temperature dial off and look at it, you will see there are two additional exposed contacts. Take the two wires off of what they're connected to and place them on those two contacts. the other option, is to just connect those two wires that are on the back of the thermostat dial in the fridge. Either one of these will effectively bypass the thermostat. I installed refrigeration on my hunter 37.5 in an icebox very similar to what you describe. I had similar symptoms two years ago, and this is what I did just to see if the compressor would kick on. It did, and the refrigerator would cool and I would then have to control it on the DC panel until I ordered a new thermostat and installed it, which, by the way, is a 5-minute job all within the refrigerator itself.

I had gotten to the boat late that night and had a week-long trip planned with all provisions.

Good luck!

[SailorMcCruise]

Ah, sorry, should have mentioned that I also tried that already with no success.

[s/v Jedi]

In 99% of the cases this is a problem with the power feed to the controller. You measure voltage when it’s idle, but when it tries to startup, voltage drops dramatically.

The contacts at the controller are suspect, as are the crimped terminals. I always have a tabletop power supply at hand for testing, I recommend that or even a small battery that you can hook up with some test leads (new crimps, 12AWG short leads)

[SailorMcCruise]

Cant seem to edit my post right now, so I just put the edits here for now:

EDITS:

- thermostat is bridged to exclude issues from that side
- the cables to the unit are 4mm tinned copper, newly crimped and I also tried with thicker ones running directly from the battery with no change in the symptoms or measurements

[sailorboy1]

Have you added any refrigerant to it recently?

[SailorMcCruise]

refridgerant was added in February with the re-pressurization of the system.

[Richard Kollmann]

Originally Posted by SailorMcCruise

Hello all,

I have been using an ice-box-converted-into-fridge system which I inherited when I bought ye olde boat i have been splashing around with.

It is based around a Danfoss BD35 compressor and a 101N0210 electronics unit.
I had posted here a while back, since the system wouldnt cool properly but it seems that this issue had been fixed after a knowledgeable fridge-repair-person did exchange the coolant and repressurized the system a few months back.

Now unfortunately the compressor stopped compressing and my champagne, my caviar and all the other unseen riches from the fridge's depths are just a shadow of their former self.

I have eagerly followed most of the relevant troubleshooting tips I have found here and would like to share the results, so I can maybe get the system running again.

Symptoms /measurements ( with bridged thermostat ):
When the system wants to start, the fan begins running and the compressor jolts once as if trying to start. The led I installed flashes three times.
The voltage going into the unit is 13.3 V, at the ( running ) fan I measure 11.7V
The voltage at the compressor cables is around 34V when starting and then drops slowly to a steady 13.3V.
After disconnecting the compressor cable I did not detect a short between one of the leads and the housing. The resistance of between the leads is around 3.5Ω

The system starts, runs for a while without the compressor, just the fan, the stops and starts again.

The compressor has some corrosion on the outside ( mine is a wet boat ) but I have no idea if the inside would look the same. see image.

If I can find a similar system I would probably try to see if my electronics unit would work with a different compressor first, to continue troubleshooting.

Thanks for all hints, ideas and suggestions.

Three LED code flashes every 4 seconds indicates compressor is overloaded during start. Most likely too much refrigerant or possibly a bad ground connection between battery and control module. A change in temperature from when refrigerant was added too and now system is much warmer will increase the volume of gas refrigerant vapor causing an over load condition on start. When last operating OK what was amp draw amps above 6.5 this would have predicted trouble in warm weather. I recommend running a new jumper wire ground first. IF new ground does not fix problem remove 2 seconds of small amounts of refrigerant with compressor stopped waiting 5 minutes each time after each start up test and try again.

If LED code displays 4 or 5 or 6 flashes every 4 seconds also run a new power wire with 15 amp fuse direct from battery to control module.

[basenay]

Have you read or watched Youtube videos on start & run capacitors? That is apparently common cause for compressors not starting as it was in my case. Few $ and easy change out by myself here in Mexico worked. Most advise change both since so they are cheap and most people can't or don't know how to test capacitors correctly. If you decide to change be sure you know how to safely discharge the capacitors by shorting as can get a high voltage shock.

[kas_1611]

We have the same compressor so this might apply, worth checking anyway.

There is a low voltage cut out that kicks in at 11.9V. It doesn't actually stop the fan running but prevents the compressor starting. Means your fan moves warm air around the fridge/cold box but doesn't actually cool anything. If you are measuring 11.7V at the supply this could be the problem.

[wingssail]

Originally Posted by kas_1611

We have the same compressor so this might apply, worth checking anyway.

There is a low voltage cut out that kicks in at 11.9V. It doesn't actually stop the fan running but prevents the compressor starting. Means your fan moves warm air around the fridge/cold box but doesn't actually cool anything. If you are measuring 11.7V at the supply this could be the problem.

I've had this exact problem. There are a few really good refer guys typically on this forum (such as Richard Kollmann), take his advice.

But I can say that the low voltage cutout is below 11 volts, I've read 10.7 or 10.4v. If you are measuring 11.7 when the compressor tries to start then this does not seem like a low voltage problem to me (nor do the number of flashes) however, as Mr Kollmann suggests, a temporary new power and ground line directly to the battery (fused) is a quick and easy test.

Otherwise the three flashes indicates a compressor overload. Releasing some gas as described might resolve this. But in my case it did not and I had to buy a new system.

I took the opportunity while the new one was being shipped to refurbish the inside of the Ice Box for better insulation, filled some gaps, put on a new finish and a flatter floor. When the new unit was installed I have cold temps and it uses less power and my beers don't fall over. All good.

[sailingchiro]

Does a danfoss compressor have a capacitor? I honestly don't know. On my rental properties, that is the first thing I replace followed by the contactor (relay), thermostat. Because in that order, they are very cheap and most common failure points. Of Course, I make sure voltages are good before proceeding. Looking at the other threads, I would change capacitor, check for voltage lag due to bad connections, short thermostat, then check for coolant levels with cheapy auto gauge and release if needed depending upon coolant type.
Wish I knew more about coolant systems on boats. Thanks for education CF.

[Juhana]

Hello,

my Danfoss unit had exactly the same symptoms, you described "The system starts, runs for a while without the compressor, just the fan, the stops and starts again.“

Problem was very simple, corrosion hiding well inside the 12v power cables. I measured somewhat decent voltage numbers, so probably there wasn't just enough amperage passing through to get things started properly. I replaced the wires and it's all good again.

So, I suggest trying with fresh pair of wires before any major operations.

Greetings,

Juhana

[Coolerking]

There is NOT a start or run cap on secop/danfoss 12/24vdc. units