Norcold BD35F Danfoss running but not cooling properly

[seasick]

Before you do anything, turn the entire unit up-side-down for 24-hours without any power applied. After a full 24-hours, turn the entire fridge right-side-up and plug it into a known good AC outlet.
I have brought at least a dozen Norcold refers back from the dead with this simple trick.

If this doesn't fix your problem and I'll be surprised if it doesn't, then what SV Third Day said.

[Lady-Lou]

I am a refrigeration tech of many years now retired and a boat owner
The symptoms are moisture in the system.
Since it is R134a the system uses poe oil, I doubt wax would be the problem.
If it refrigerates properly in the beginning that indicates a proper gas charge. Moisture in the system will accumulate and freeze at the first point where the temperature drops below freezing and take some time to accumulate enough moisture to totally restrict the capillary tube.
You will notice a small refrigerant filter dryer on the condensing unit where the capillary tube starts, its purpose is to remove moisture and particulate matter which could cause a restriction in the tube. As the ambient temperature increases the dryer will release some of the moisture it has accumulated and cause this problem, we are talking minute amounts of moisture. i suspect there was more moisture in the system from startup than the dryer could successfully handle.
Now for the fix: install schrader charging tube on the discharge side at the compressor, then you should replace the refrigerant dryer and evacuate the system to a 100 microns or better to remove any residual moisture in the system, or, just evacuate the system to 100 microns and hope it will not happen again, then recharge refrigerant by weight and close charging port.
I think you are getting hung up on the electrical side of things and from your info I do not see any problem there as you have indicated that the compressor is operating at all times.
Remember: make sure you use an electronic vacuum gauge when evacuating the system as I can not stress this enough, any competent tech will have the proper equipment. Shut off line to vacuum pump and make sure the proper vacuum is maintained.
If you decide to change the refrigerant dryer (recommended) the system MUST BE PERGED WITH NITROGEN BEFORE ANY SOLDERING IS DONE. This prevents oxidation of copper on the inside of the pipe to cause further restrictions in the capillary tube. Any shortcuts to this procedure will cause problems and cost you money.

[actionpaintball]

Seasic: what is the basic reasoning on why that might work? (tipping it upside down?). I will definitely try that 1st...easy test. And thanks for info on the moisture, that will be my last effort after trying to diagnose the controller.

[newhaul]

One lil thing to think about with advice know the poster try the inverted bit then follow Richard kolleman or rich. Over at SV third day. Those guys make their living building and servicing our 12v. Marine refer systems

[Richard Kollmann]

Actionpainball, see what I mean about damaging destructive good intention recommendations offered before confirming what is causing your problem. The Danfoss BD is a smart electronic compressor that can be expected to perform well for 30 years or more.

As to use of a volt meter to test safety logic circuits in module forget it. You can test resistance of the three coils inside compressor to see none are grounded and pair of all three pins have equal resistance. The older BD compressors had two field coils and an internal transducer coil to maintain 2500 rpm by using chopper transistors to reverse current to a low voltage wave cycle. These new compressor external modules control armature rotation and variable speed based on milliamps of current flow through thermostat circuit. With no resistance in thermostat wire five milliamps of current will run compressor at minimum 2000 rpm By increasing resistance to 1500 ohm compressor will run at 3500 rpm. By voltage pulse changes to field coils speed is compressor controlled. By monitoring fan amps, voltage and module amps theses safety circuits will stop compressor if power exceeds normal limit ranges.

I am retired and no longer in boat refrigeration work. But I do test modules at no charge you pay only shipping. If module is good I return them insured Priority mail cost is $20.
If Module is bad I have new non Danfoss modules you can try on your unit I can loan or sell you a module You pay shipping and if your unit damages my module still all you pay is shipping.

[actionpaintball]

wow! That sounds great. Should I try the tipping-it-over for 24 hours first? Thanks for all the help.

[SV THIRD DAY]

So here I am working on painting my boost stripe in the boat yard yesterday when I get the same type of call I get almost weekly, it goes like this:

Client: Hey Rich, I need to buy a new compressor/condensing unit, mine died.
Me: Can I ask you why you think your unit is dead?
Client: ya, it won't start up and my dock neighbor knows about refrigeration came over and said it was dead.
Me: Do you mind if I ask you a few questions and give you a few tests?
Client: Well, ok. But my buddy is an expert and already did all the known tests.
Me: I'm sure he is, but just humor me. So can you first run a temp DC power line right from your battery plus and minus terminals to the black box controller on the compressor?
Client: man, that's a pain in the ass and I checked voltage with my volt meter at the unit and it says 12.3v and my volt panel on the ships display says 12.9v, so I don't have a voltage issue.
Me: I understand it may look that way, but trust me, I go through this all the time and I don't want you to buy a new compressor/condensing unit if you don't really need one.
Client: well ok, I will do it, but I'm telling you, my boat has the most beautiful wiring you have ever seen. It just can't be my million dollar boat's wiring.
Me: well do the test and call me back even if it's a Sat or Sunday I will be here.
Client 45mins later: Well I'll be damned...when I wired the unit straight to the battery it fired right up, I can't believe it. So then I started looking around and found that the power panels ship ground was loose and when I fixed that, now my unit works. Thanks a lot for saving me $1495 on a new unit!
Me: You are welcome amigo....now back to painting.

That's the norm....
The problem is (as Richard points out) there is no in the field test to see if your controller has failed/burned out and died. You have to arrive at that determination by the process of elimination or by swapping out a known good controller.

[motion30]

I'm not sure Tipping it over is a good idea, I've seen domestic refrigerators transported on their side that never ran again.
what do the experts here say?

[SV THIRD DAY]

Originally Posted by motion30

I'm not sure Tipping it over is a good idea, I've seen domestic refrigerators transported on their side that never ran again.
what do the experts here say?

Never knowing when it's best to just shut up...I'll bite.

At first it though it was some kind of joke post, like wrapping the compressor in bacon and burying it under a dead chicken during a full moon for 24hrs to expel the evil spirits.

Being serious for a moment, I'm always open to new fixes but I just can't see how this could "fix" a compressor problem. A Danfoss compressor is a Danfoss compressor regardless of the brand of refrigeration system it is installed in, and we have never advised anyone to turn it upside down to fix something.

I need a drink and it's not even noon here.

[Richard Kollmann]

No, Do not turn unit upside down. You do not have an RV heat absorption refrigerator.
Turning refrigerator upside down will only allow 12 ounces of oil to seek space in low pressure side of system and possibly damage compressor valves the next time compressor is started.

[actionpaintball]

I have it on my garage bench wired to a newish optima battery with 5 foot leads. 13.5 volts and tested to 650 real life amp draw. I have done 75% of my testing plugged into 110 AC... Should I be doing all my testing on the 12 volt battery? I have also swapped batteries and it did not help. I am going to do resistance test on the compressor coils and then get the controller tested.

Last night it was defrosted and unplugged, I then plugged it into 110 AC when I was doing some other work in the garage; the IR gun readings were 20 degrees F (freezer) and 42F (fridge) after about 30/40 minutes. 3 hours later compressor was running and freezer was 36 and fridge was 49. I had the setting on 5. When its cold (ie 20/45) the thermostat will shut off the compressor at about the 3 setting.

Not going to do anything crazy, just get the controller tested...

[Richard Kollmann]

I do not know What you mean "13.5 volts and tested to 650 real life amp draw."

Normal testing of your unit would be to test first on 110 volts with control knob set to max cold for 12 hours.
Then repeat test with no 110 volt power only 12 volt DC.

In both tests evaporator should have evaporator 90% covered with a thin layer of frost and box temp very cold. If this is true there is no need to test module.

If box does not get cold enough test thermostat by placing a jumper wire on module between C and T terminals and let unit run for at least 12 hours.

If thermostat tests good unit is normal. To test further leave on bench for a week running with thermostat set in mid range.
Place a standard open container in freeze section and when frozen turn it over if in a week the ice is still in container refrigerator and refrigeration unit is in good working condition. This would indicate there must have been a problem before with boats electrical system.

[actionpaintball]

"13.5 volts and tested to 650 real life amp draw." Meaning I put a fluke meter on the battery, it tested at 13.49 Volts. I then put an amp load meter on the battery and the needle stayed on 650 amps....meaning I load tested the battery (just ensuring the battery was good).

[actionpaintball]

The box gets cold in both instances...the problem I seem to be having is that the freezer totally defrosts and the compressor runs almost the whole time. On both 110 AC and 12vDC the plate will frost to 90 to 100 percent and freezer temp will get to about 20 degrees. Compressor stays running and the plate will then start to warm up to about 35/40 degrees before it starts the cycle again.

[Lady-Lou]

All indications are moisture in the refrigerant circuit. When it warms up after freezing the moisture thaws and allows the system to commence working again until the moisture refreezes in the capillary tube. My original post still applies.