Dometic Cff35 - Wild Swings In Temperature

I have had three cooler-style fridges - so I'm not new to their behavior. But my CFF35 seems different...

If I put the fridge in the open, it will hold the temperature well. If I set 36, it will stay between 34 and 40. So, I suspect the thermistor is working correctly.

However, if I restrict airflow by putting it in the galley, I see a temperature decrease in the chest. Not a rise as I would expect. Overnight, I will see temperatures well below freezing --- I set it at 36, but I'll have 24 or 26 degrees meaning frozen meat and eggs.

My CF35 would get warmer in this same situation, which made sense, as moving the heat from the inside of the cooler to the outside is more difficult than to space with good ventilation.

I'm puzzled by this --- I would EXPECT with restricted airflow that you would see higher internal temperatures, not lower ones. Is anyone else seeing something like this?

 

Just replaced the thermistor...I'm happy to say on the CFF35 it is even easier than the CF35.

about 13 screws to remove the sheidl around the compressor area, 2 screws that hold the cable security inside. There's a gummy seal to keep moisture out...just give it a gentle tug and the part pops right out. Beyond that its cutting a zip tie and inserting the plug into a socket. All told, took about 15 minutes to do.

See if it works. Both thermistors showed the same resistance ... ~10k ohms, hopefully, this one (the new one) doesn't flake out and keeps the temperature set without reporting falsely high temperatures to the controller.

Testing is under way...

 

Just a quick upate on this. I have an ARB 47 refrigerator, which is _remarkably_ similar to the Dometic/Waeco and probably most of the compressor based fridges out there.

Disappointingly, the reliability of the parts is equally poor in design. If I were a betting man, I would imagine it is moisture that makes it way to the electronic component itself. The rule is --- Water always win.

I suppose the one bit of good news is that the thermistor is easy to replace, at least on the newer ARB and Dometic (I believe older units embed the thermistor deep, requiring cutting and removal of spray-foam insulation, and we know how hard that is!)

The ARB Part number is : 10910027

ARB is slightly more friendly towards repair than the Lippert-opened Dometic, you can find the service manual if you look online (Minimum Stocked Spare Parts - ARB 47L Service Manual [Page 10])

Repair time on the ARB was about 15 minutes plus verification, which is going on right now. I'm getting, sadly, pretty good at this repair. I keep 2 of these thermistors on hand at all times now.

EDIT: I got mine from Summit Racing. In the past, they were a "drop ship" company meaning they'd show it in stock, but it did not exist in their supplier inventory. I ordered 2 and have a tracking number. If you're desperate PM me. They cost me $16 a piece and I'll be glad to share if you can't find them as long as I have one on hand.

EDIT EDIT: Shocking! Showed up today, have to say for a racing equipment company, the shipped fast! I have 2 extra thermistors on hand....ready for the 15 minute job to return a fridge to working again. Danfoss, I'm ready for your sudden but inevitable betrayal!