Dometic Cff35 - Bad Thermistor?

[Forrest J Hodgkins]

We recently had some operational problems with our Dometic CFF35 refrigerator (ie, freezing entire contents even though setpoint was 46F), and the internet posts all seemed to point to a failed/failing thermistor. This became more involved than I originally expected, and so I thought I would share my findings.

Is my thermistor bad: I removed the bottom venting enclosure surrounding the compressor and controls, and was able to easily get access to the thermistor 2-pin connector. It read about 11 k-ohms resistance. But I had no way of knowing if this indicated good or bad thermistor.

Replacement thermistor: Dometic website refers you to local RV dealers for replacement parts, but the 3 dealers I spoke with all reported they were unable to determine correct part. A call to Dometic customer service revealed the proper part number for thermistor for this refrigerator: 4450001983. They did not have it in stock, but I found one at rvpartsexpress.com. I measured resistance of new unit, and it matched my existing thermistor.

My solution: since existing thermistor checks out electrically, I pulled it out and saw that there wasn't complete coverage with thermal paste, so I added as much thermal paste onto the tip as I could, and re-inserted it, and closed everything back up. Running the Dometic for several hours shows it is now tracking to the setpoint properly, and I now have a spare thermistor for that day in the future when current one fails.

 

[Sweeney]

We recently had some operational problems with our Dometic CFF35 refrigerator (ie, freezing entire contents even though setpoint was 46F), and the internet posts all seemed to point to a failed/failing thermistor. This became more involved than I originally expected, and so I thought I would share my findings.

Is my thermistor bad: I removed the bottom venting enclosure surrounding the compressor and controls, and was able to easily get access to the thermistor 2-pin connector. It read about 11 k-ohms resistance. But I had no way of knowing if this indicated good or bad thermistor.

Replacement thermistor: Dometic website refers you to local RV dealers for replacement parts, but the 3 dealers I spoke with all reported they were unable to determine correct part. A call to Dometic customer service revealed the proper part number for thermistor for this refrigerator: 4450001983. They did not have it in stock, but I found one at rvpartsexpress.com. I measured resistance of new unit, and it matched my existing thermistor.

My solution: since existing thermistor checks out electrically, I pulled it out and saw that there wasn't complete coverage with thermal paste, so I added as much thermal paste onto the tip as I could, and re-inserted it, and closed everything back up. Running the Dometic for several hours shows it is now tracking to the setpoint properly, and I now have a spare thermistor for that day in the future when current one fails.

Hey moderators, how can we get this guys Newbie badge upgraded with an honorary title?!

Great post Sir! Welcome...

I have a similar post about my CF35 doing the same thing happen, although my thermistor was actually bad. When mine failed the compressor ran full speed for a couple days and the scroll compressor met its match...it was unable to reliably cool even after the electronic problem was resolved. Now, we now have a CFF35 as well.

While it was a pricy experience, I have to say the CFF35 is better in just about every way...no metal rivets inside the chest, seems to be more evenly cool throughout, more space...just a nice fridge.

 

[Cary Winch]

Excellent write up Forrest! I am glad you were able to diagnose this. This will help others in the future for sure, this should be an important go-to post on the forum.

Cary

 

[dmb]

Thank you so much for this post! I've been having the same problem. After freezing things to death, my CFF35 has since displayed an "Err2" and refuses to operate. Following your advice, I tried re-applying thermal paste to the thermistor but the error persists. I spoke to Dometic and they confirmed the error is likely a result of a bad thermistor and graciously agreed to send me a complimentary replacement.

While I'm waiting for the replacement, I was wondering how you accessed the 2-pin connector? It looks like it just feeds into the compressor control module — a literal black box with no obvious screws to unscrew — with a bunch of other wires. Did you need to pry off the cover of the control panel to replace the thermistor? Thank you!!

 

[Sweeney]

ERR2 tells me the thermistor itself has failed. If you have trouble finding them, I'll see if I can, let me know.

Its beena while but you shouldn't have to pry anything - it all comes apart easily. For what it is wroth, the black putty that they use is sticky and remains plyable -- if you remove it carefully and with gloves (and don't drop it in sawdust --- don't ask ) its reusable....just form it tightly. If you DO drop it you can use Butyl tape - DM me if you need some, just DM me.

The thermal paste is the really only nasty stuff -- I havn't got a good solution yet. I'm a bit lucky that I periodically run into the stuff --- its called thermal mastic and sells for about $65 for a tube of it -- the caulking tube size. Dometic uses this stuff in their absorption refrigerators...Its a prescious commodity

 

[JohnC]

When I had that problem they graciously offered to send me the part and some instructions on how to fix it myself. I graciously told them I don't think that's how warranties are supposed to work. They then graciously sent me a new fridge.

 

[Sweeney]

DId they ask you to "field destroy" the old one?

 

[JohnC]

DId they ask you to "field destroy" the old one?

No. They just told me to remove the sticker with the bar code, place it on a piece of cardboard and send them a photo. They probably marked it in the system so it can't be claimed for warranty again. I've been keeping it for backup and ended up having to use the "old" electrical cord on my "new" fridge when it quit working properly. Apparently cords going bad are another Dometic known problem.

Last year I bought a 23qt Bouge RV for about $160. Only used it on my long trip (23 days 2000 road miles) earlier this year but it worked fine.

 

[Jenn]

My dometic started that "will only freeze everthing" activity. I thot it was because of being bounced around the back of the teardrop for too long. So I just use it for a freezer at my summer camp. I also just got the BougeRV fridge. It's wonderful.