Dometic Automatic Temperature Control

[wiredgeorge]

Have an old 2002 Cougar 5th wheel with the original Dometic Automatic Termperature Control 2-door refrigerator. Most folks complain things don't get cold enough. Opposite problem here. Water bottles left on racks on refrigerator door will freeze solid and a case of Coke in the main compartment get ice in them. This particular model refrigerator DOES NOT have the temp adjust slide on the upper right side near cooling fins. Anything that can be done to moderate the temp? TIA. wg

[chuckster57]

It should have a thermistor, and I would try changing it. When we diagnose poor/no cooling, part of the process involves unplugging it forcing the cooling unit to run “wide open”. Not saying that’s your issue, but it may be worth changing.

[JRTJH]

If I recall correctly, our Dometic refrigerators from that era all had thermistors. It may be that the previous owner bypassed it or just ripped it out which would cause the refrigerator to go into limp mode and never shut off. That would cause your problems with freezing.

You can download the Dometic Americana Refrigerator service manual here: http://www.fourwh.com/NewDometicRefrigeratorManual.pdf

Page 11 has instructions on how to troubleshoot the thermistor from the circuit board back to the actual thermistor (which may be missing on yours), so those steps may get you headed in the right direction.

Let us know what you find.

[wiredgeorge]

Thanks. Was unfamiliar with a "thermistor" as I have never had an issue with any of the RV fridges I have owned. Seems you can move the pickup end to control the temp some as well. Will see if I can locate the circuit board and test the thing and try moving it as suggested in some how-to write ups I saw online.

[wiredgeorge]

OK, got to look into thermistor mystery today. The wire comes out from the back of the fridge through the back wall. The wire was hanging straight down and about a 1/3 was not pulled through or had been shoved back. In any case, I found a small plastic bit that is obviously used to clip the thermistor to a cooling fin and a search of the internet indicated the farther up and to the right in the refrigerator compartment (clipped to a fin) the warmer the fridge. There doesn't seem to be a bunch of temp range from what I read but I put the wire in the clip and clipped it to the upper right fin about as high as it will go. I am going to see if this moderates the too-cold temps so stuff doesn't freeze. If that doesn't work I will either test or replace the current thermistor.

[JRTJH]

Dinosaur Electronics builds a series of control boards for RV use. They include refrigerator, water heater, furnace control boards and they typically are "hands down" better than the OEM boards both in function and in reliability.

Dinosaur has come out with a "Dometic thermostat" to replace the thermistor in RV refrigerators. Instead of having a "fin slider" to control temperature, there is a rotary knob to "dial in the correct temperature". If you're replacing the thermistor, it'll cost around $28. The Dometic thermostat is $35 and will give you significantly better control of your refrigerator temperatures.

You can read about it here: https://www.rvautoparts.com/Dinosaur-Electronics-Thermistor-Simulator-THERMISTOR-SIMULATOR_p_11600.html?gclid=EAIaIQobChMIoPXRj7_52 QIV1LjACh2ckg0pEAQYAyABEgIvdPD_BwE

[chuckster57]

Doesn’t moving the thermistor up make the fridge COLDER?

[wiredgeorge]

Doesn’t moving the thermistor up make the fridge COLDER?

According to this article, moving up and to the right warms and down/left cools.

http://rvrefrigeratorrepair.com/uncategorized/the-thermistor-shuffle/

[wiredgeorge]

Dinosaur Electronics builds a series of control boards for RV use. They include refrigerator, water heater, furnace control boards and they typically are "hands down" better than the OEM boards both in function and in reliability.

Dinosaur has come out with a "Dometic thermostat" to replace the thermistor in RV refrigerators. Instead of having a "fin slider" to control temperature, there is a rotary knob to "dial in the correct temperature". If you're replacing the thermistor, it'll cost around $28. The Dometic thermostat is $35 and will give you significantly better control of your refrigerator temperatures.

You can read about it here: https://www.rvautoparts.com/Dinosaur-Electronics-Thermistor-Simulator-THERMISTOR-SIMULATOR_p_11600.html?gclid=EAIaIQobChMIoPXRj7_52 QIV1LjACh2ckg0pEAQYAyABEgIvdPD_BwE

Looked at the Dinasour gizmo and it states on their website (not the seller you listed) that it is for when the refrigerator is NOT COLD ENOUGH which is opposite of my issue. Put some water bottles back on the shelf after relocating the thermistor pickup in my refrigerator and will know in a day or two if this was effective. BTW: The Dinasaur gizmo goes inline with the OEM Dometic thermistor wire and provides temp changing ability so might be a great answer for someone. Thanks wg

[wiredgeorge]

Follow up! Seems clipping the thermistor probe end to the upper right fins inside the fridge did the trick. No frozen water bottles! Thanks to all for the tips!

[chuckster57]

According to this article, moving up and to the right warms and down/left cools.

http://rvrefrigeratorrepair.com/uncategorized/the-thermistor-shuffle/



This is a picture from a 2018 trailer with a Dometic auto temp refer:
https://uploads.tapatalk-cdn.com/20180328/4557b10a8b55c68d4bec4cb1ccba3678.jpg

Just sayin....

[wiredgeorge]

I have owned a number of Dometic refrigerators with the arrow and plastic piece that slides holding the thermistor. On my current refrigerator, no arrow. I didn't notice the thermistor hanging down towards the bottom nor notice the plastic bit in one of the bins. I have since installed the plastic bit and the thermistor is placed where the current inside refrigerator temp is pretty much spot on. Thanks.