RV Refrigerator Problems

[rthomas]

Has anybody had experience getting help to diagnose a Dometic RV refrigerator problem. Mine cools on gas and 120V, but not 12V. It's a very old (1986) unit.

 

[DavidC]

The one's I have heard of usually involve the circuit board. This place I believe either supplied the replacement or repaired the card.

Dinosaur Electronic's 3850415. 01 replacement page



Dave

 

[SierraRam]

Never seen a 12 volt only before. Usually gas or 120vac. Of course you need 12vdc to run on the gas mode.

 

[GCroyle]

Wiring diagram, multimeter test. Is 12V being supplied to the heating unit? Disconnect 12V wire to heater, check resistance of heating unit, specifically is it an open circuit at the heater?

 

[bheiting]

Have you read the manual? Mine does not recommend starting the initial cooling on 12V. Start with 120V or gas and then maintain the temp. with 12V. Apparently 12V is not as efficient as the other sources.

 

[Bill Stockard]

Wiring diagram, multimeter test. Is 12V being supplied to the heating unit? Disconnect 12V wire to heater, check resistance of heating unit, specifically is it an open circuit at the heater?

Yep, it sounds like the 12-volt heating coil is burned out. Here is a web site with very good trouble shooting information on RV refrigerators: RV Mobile, RV and Gas Refrigerators



Bill

 

[rthomas]

Thanks to all for the help. I was able to get to the RV Mobile site and got a generic wiring diagram. I isolated the 120V and 12V heater leads and determined that the heaters were OK. That is both had finite resistances of about the right values for the nameplate current. (1. 13 Amp on 120, 11 Amp on 12V). I also discovered that with the selector switch on 12V and with a good battery, there was no voltage at the 12V heater terminals. So I guess the problem is in the selector switch. The unit is over 25 yars old, so the manual is long gone. But I always start it on 120V before trip start and used to switch to 12V while on the road. I now have to use gas while on the road and amazingly the burner stays lit even at freeway speeds. Using gas on the road is probably a safety issue though. replacing the selector switch looks like a big deal ($$$) so maybe a new refer is in order, but does it make sense to put a new refer in my 25 year old Lance model 300 Camper

 

[Road Dog]

I never bothered with the 12VDC setting and new fridges don't offer it. The fridge stays cold for a long time (8hr) but your mileage may vary. I always turn off the propane when driving and if you've ever seem the end result of a propane explosion (bits of camper spread far and wide) you would too.

 

[Bill Stockard]

I never bothered with the 12VDC setting and new fridges don't offer it.

Lance still installs three way (120 volt AC, 12-volt DC, and LP) fridges in their 2012 models. The refrigerator will automatically switch to 12-volts DC if 120-volts AC and LP gas is not present and if it is in the "Auto" (automatic) mode. My '03 Lance fridge operates the same way.



Bill

 

[Bill Stockard]

replacing the selector switch looks like a big deal ($$$) so maybe a new refer is in order, but does it make sense to put a new refer in my 25 year old Lance model 300 Camper

It might be easier and less costly to wire around the selector switch using another switch. I wouldn't worry too much about keeping the thermostat in the circuit since it probably won't cool enough running on 12-volts DC to freeze the contents in the fridge.



If you decide to replace the fridge, take some measurements. You may discover that you will have to partially disassemble the old fridge to get it out the door and partially disassemble the replacement fridge to get it inside the camper.



Bill

 

[jeepit]

Lance still installs three way (120 volt AC, 12-volt DC, and LP) fridges in their 2012 models. The refrigerator will automatically switch to 12-volts DC if 120-volts AC and LP gas is not present and if it is in the "Auto" (automatic) mode. My '03 Lance fridge operates the same way.



Bill

Mine is the same!

 

[EricBu12]

The old 122001 volt units were a joke even back then. . that is why all you see is gas and electric. . for the problems and cost it would be better to replace it with a modern one. .

 

[Bill Stockard]

The old 122001 volt units were a joke even back then. . that is why all you see is gas and electric. . for the problems and cost it would be better to replace it with a modern one. .

Yes, the 12-volt DC element wasn't very effective in a trailer since the fridge is located so far from the tow vehicle battery/alternator. A properly wired truck camper fridge works much better on 12-volts DC since it is located much closer to the truck's battery/alternator and much less voltage drop through the long wire harness. Most trailers aren't wired at the factory with 8-gauge wiring to the fridge including the receptacle/plug like a Lance camper.



Bill

 

[GCroyle]

I have a 2007 Dometic 2 way power fridge and I have learned a lot about it, but I'll complete that by saying I haven't learned ENOUGH about it.



These things are weird.



They (according to public theory that I have read about) like to be beaten with a stick or rolled on the ground, really level for operation, fooling the thermister, adding some type of additional air flow on the upper coils, don't forget checking your LP pressure and then hedging your bet with extra frozen foods transfered to the refer compartment.

 

[JMetzger]

Gary you are right. The best thing I did was put a muffin fan at the top of the exhaust above the fridg to remove the heat. Knock on wood our fridg is original in 96 with no repairs, I lay it to removing the heat from the compartment.

 

[Bill Stockard]

I have a 2007 Dometic 2 way power fridge and I have learned a lot about it, but I'll complete that by saying I haven't learned ENOUGH about it.



These things are weird.



They (according to public theory that I have read about) like to be beaten with a stick or rolled on the ground, really level for operation, fooling the thermister, adding some type of additional air flow on the upper coils, don't forget checking your LP pressure and then hedging your bet with extra frozen foods transfered to the refer compartment.

:-laf:-laf

Gary, you pretty well summed it up. 19th century absorption design with 21st century controls...



I don't know why the RV industry doesn't move into the 21st century and install fridges with the energy efficient 12-volt DC Dan Foss compressors that draw only about 4-amps when running on 12-volts.



Bill

 

[GCroyle]

Bill,



Did I mention that my 1-2-3-4-5 control lights have flashed in sequence as I changed the setting and on an RV forum NOT ONE person responed with the, Yeah mine used to do that comment! I had to turn it off and walk away, sneak up on it and start it again before it know it was me. I also had the draft recall done, cleaned the orifice and shot the back side with my temp gun ad infinitum trying to learn its inner being.

 

[RBellah]

What about the fuses? Some of the models have old style automotive glass type fuses on the lower circuit board. Probably a 3 or 5 amp fuse. I believe you take the outside panel off to get to it.

 

[Bill Stockard]

What about the fuses? Some of the models have old style automotive glass type fuses on the lower circuit board. Probably a 3 or 5 amp fuse. I believe you take the outside panel off to get to it.

The original poster's fridge is a Dometic pre-circuit board type 3-way. There are two fuses in the system. You are correct about the glass type fuse. One is 3 to 5-amp for the 120-volt AC heating element circuit and one is 20-amp for the 12-volt DC heating element circuit. There also could be a relay in the 12-volt DC circuit that is operated by the thermostat. Changing modes, LP, AC or DC is done manually through a mechanical selector switch located at the bottom of the fridge. There is also a manual spark ignitor button when switching over to LP in the same area. It is a simple and very easy to troubleshoot/diagnose control system.



Bill