Dometic RM77 is tooooo cold....

[mountainman1]

I have a 1976 Overlander AS containing the original Dometic RM77 Gas/Electric Refrigerator. This refrigerator works too well and will freeze food after while on gas or electric. Nowhere does it state wheater number 1 or 6 on the dial is the coldest or warmest setting. I tried setting it at 1 and then 6 and still get 20 degrees in the refrigerator after a few days of running. Also frost builds up on the cooling fins in the back inside the refrigerator compartment. I have no problems with the freezer unit but I'd like to have non-frozen lettuce in my salads. I have also noted a faint smell of propane around the unit at times. The owner’s manual states the flue could need a cleaning but doesn’t state how to do this??? Any help would be greatly appreciated.

Mountainman1.

[easyride]

I had one where the sensor was not touching the coil correctly,and it would get too cold.
Hope that`s all it is. Dave

[mountainman1]

Thanks for the help Dave. I have a parts schematic of the refrigerator. I'll look it over and see if I can find where this sensor is located. That sounds very logical since the problem is associated with both the electric and gas functions.

[Inland RV Center, In]

Originally Posted by mountainman1

Thanks for the help Dave. I have a parts schematic of the refrigerator. I'll look it over and see if I can find where this sensor is located. That sounds very logical since the problem is associated with both the electric and gas functions.

The higher the setting, the colder your asking the reefer to get.

Broken thermocouples are the usual cause of "no temperature control", as they can no longer send the information to the thermostat, which then allows the cooling to go to the maximum.

Thermocouples look like a small single wire, that goes from the thermostats to the inside of the reefer where they sense the temperature.

Andy

[mountainman1]

Thanks Andy. Ok, I found the thermocouple wires. There appears to be two wire coming into the refrigerator compartment and it looks like one goes to the electirc controls and the other to the gas control on the back of the refrigerator. Do you know if these thermocouple wires are easily replaced? This would also explain why changing the settings on the contols, gas or electric, makes no diffrence on the temp in the fridge.

[Inland RV Center, In]

Originally Posted by mountainman1

Thanks Andy. Ok, I found the thermocouple wires. There appears to be two wire coming into the refrigerator compartment and it looks like one goes to the electirc controls and the other to the gas control on the back of the refrigerator. Do you know if these thermocouple wires are easily replaced? This would also explain why changing the settings on the contols, gas or electric, makes no diffrence on the temp in the fridge.

Sorry, but the thermocouple is a part of the thermostat, and cannot be replaced by itself. Thermocouples also have a liquid inside that small tubing that looks like a wire.

That liquid is usually mercury.

Andy

[easyride]

The sensor or thermocouple,comes from the control valve to the inside of the fridge,then clips on the coils in the back of the refrigerator. Dave

[mountainman1]

Dave, I tried what you said. I repositioned the end of the capillary tubes inside the refrigerator compartment. I pushed then up higher in their bracket which is attached to the fresh food evaporator. The refrigerator has been running for a day now on control setting 4 and the internal temperature is staying between 34 and 38 degrees. It's currently running on electric and I'll try the gas setting in a couple of days. Thanks for the suggestion.

[joelreh]

I was having a similar problem a week or two ago with the original dometic in my '73 overlander...but for some reason it doesnt seem to be freezing anymore and i did nothing to it except fiddle with the dial (its on electric...havnt had the courage to try the gas yet). So really I have nothing of value to add to the thread except my thanks for giving me some troubleshooting ideas should it act up again.

[tamo2000]

Hi,
similar type of issue: The orig. RM77 in my Overlander gets too cold - on electric and gas.
I removed the capillary tubes and fixed them again as suggested before. I took of the thremostat/thermocouple and cleaned it.
About the gas:
The flame stays constantly high - even if I turn the gas temp. control to "off".

Any suggestion how to verify that the capillary tubes did not loose they pressure?
Any idea where to get spare parts?
Here some details:
Gas thermostat Nr. 289003103, RANCO made in UK.
Electro thermostat Nr. 289003203

Any help appreciated. I also attached photo from the gas thermocouple.

[Inland RV Center, In]

Originally Posted by tamo2000

Hi,
similar type of issue: The orig. RM77 in my Overlander gets too cold - on electric and gas.
I removed the capillary tubes and fixed them again as suggested before. I took of the thremostat/thermocouple and cleaned it.
About the gas:
The flame stays constantly high - even if I turn the gas temp. control to "off".

Any suggestion how to verify that the capillary tubes did not loose they pressure?
Any idea where to get spare parts?
Here some details:
Gas thermostat Nr. 289003103, RANCO made in UK.
Electro thermostat Nr. 289003203

Any help appreciated. I also attached photo from the gas thermocouple.

If the source of heat does not cut back, then either the thermocouple is misplaced in the reefer, or it's bad, and/or the thermostat can also be bad.

There is no other control over the heat sources.

Andy

[mountainman1]

Here's the service manual for the R77 including a troubleshooting section. Hope it helps to solve your issue.