The 32 degree problem

[Spartanguy]

I am having one of my first true “issues” on my 2015 25’ FC. I’ve read up on this and wondering if anyone here might have additional advice. After taking my AS home for Thanksgiving I developed the problem where my Dometic thermostat is stuck on 32 degrees. In any function, AC, HP, furnace it reads 32 degrees as the temperature. This means that I can’t just leave the furnace set at 60 when I’m off to work and definitely can’t forget to turn it off before bed or I will bake. Since I’m a full-timer this is also going to complicate my winter living plan. So to explain further, the thermostat will read a proper indoor temperature, but only when turned off. When turned on in any function is reads only 32.

The fixes online seem to be:
1. Make sure not set to celsius, check.
2. Do a hard reset by holding the MODE and FUNCTION key in the off position, check.
3. Flip the breaker just to try, no change.

Other solutions involve replacing the thermostat, although someone reported that didn’t even fix the problem.

Another person in the forum history says there are telephone like wires that corrode and need replacing.

Has anyone experienced this? Any additional fixes to try before I start removing walls or spending major money?

Happy Thanksgiving!

Russ

[Spartanguy]

Correction, the reset is to hold the ZONE and MODE buttons in the off setting, done this no fix.

[Foiled Again]

Unplug the thermostat from the wall. Wait 60 seconds. Plug in and try again. Can't hurt.

[drbrick]

Have you tried contacting Airstream Inc jackson cente at 1-877-596-6111 or email support at: https://support.airstream.com/hc/en-us/requests/new I have always found them to be helpful???

[Spartanguy]

Originally Posted by drbrick

Have you tried contacting Airstream Inc jackson cente at 1-877-596-6111 or email support at: https://support.airstream.com/hc/en-us/requests/new I have always found them to be helpful???

Yeah, both Airstream and Dometic closed for the holiday. Will try them again on Monday.

[Rich W]

Looks to me like it's stuck on Celsius. 32 C = 90 F. HOT! I would say the 'set' temperature is 32 C and when turned on the furnace is trying to reach that point. A/C probably doesn't even kick in, does it?

The wires in a 2015 shouldn't be corroded although there may be a bad connection. Arm chair diagnosis says it's a bad thermostat. You could get an electric space heater to hold you over until Monday, if you're on shore power.

[Adventure.AS]

Have you turned the use/store off to remove 12v power to the thermostat? After turning it back on it may reset.

[Mike1997]

My Dometic tstat is older than yours (4 button) but I also experienced problems with the furnace operation. All else worked normally. The end result which will get me through the winter (full timer also) was to put the furnace on a residential tstat with the glass bulb. Works like a charm now but planning to replace the whole system next spring.

I also replaced the Dometic tstat with a rebuilt model but it did not help. Person who helped with my change out said the old telephone wires were suspicious. He felt there was an issue with it as well.

[Spartanguy]

Originally Posted by Adventure.AS

Have you turned the use/store off to remove 12v power to the thermostat? After turning it back on it may reset.

No, but great advice. Unfortunately, past that point, will update in a second.

[Spartanguy]

Originally Posted by Foiled Again

Unplug the thermostat from the wall. Wait 60 seconds. Plug in and try again. Can't hurt.

Well, this is the advice I took. Unfortunately, I did this too aggressively and destroyed the control panel. All of this has given me an excuse to buy the newer black model thermostat I prefer the look of. Interesting to see the telephone chord connection.

[Spartanguy]

Also, DOMETIC where are you? While reading the reviews for my new thermostat ($115) I encountered another person with this problem. If you research it, this is clearly a problem and no we don’t have it set on Celsius.

[ckerrick]

I experienced the 32 degree problem with my Dometic thermostat for 2-3 weeks this fall while camping in very cold weather at Henry's Lake in Idaho. Inside temp was stuck on 32 degrees on the the thermostat, so the furnace wouldn't shut off unless I turned off the thermostat. Interestingly though... with thermostat switched off, the thermostat showed accurate inside temperature when that button was pressed. Turn the thermostat on, and inside temperature always registered 32 degrees. Some pretty cold nights without being able to maintain a minimum temperature using the thermostat; as outside temps were in the teens and into single digits for a few nights. Like others, I tried resetting the thermostat following owner's manual instructions, disconnecting/reconnecting the phone cord connector on back of thermostat, and putting trailer power switch to Store position to shut off all power to thermostat. None of these measures resolved the 32 degree inside temperature problem.

Now that I'm back home in Southern California, the thermostat returned to normal working condition after 3-4 days of 70-80 degree temperatures. Inside temperature now registers accurately and furnace and air conditioner both work properly with the thermostat. But... I'm a little apprehensive about my early April fishing trip into cold weather again since I don't know what causes the problem, nor if/when it will reappear.

I'm sharing this so my problem is also known to the community and maybe we can eventually get Dometic or Airstream to acknowledge/diagnose this problem and come up with a solution. My trailer is a 2013 25' Intl.

[Spartanguy]

Thanks for the comment, cherrick. I think it’s so strange it reads the proper temp when turned off, indicating the thermostat is working. Others report it resolving naturally, no luck with that here.

[Rich W]

If it's not working with the inside AS temperature really low, but works OK in 70-75 interior temperatures, then the circuit board must have a failing component or poor soldering joint somewhere. The metal is shrinking in the cold temp and not making contact. If you have shore power you may be able to prove this by using a hair dryer to heat up the thermostat before you turn it on. In any event, I would replace it.

[Dixie2019]

Hey Russ - I had a similar problem last winter. The problem was not inside but outside. There was a short on the roof of my 20FB FC that was created during a rainstorm when water pooled in an impression on the roof where the wiring was exposed. When the temperature dropped the water froze creating a semi-permanent electrical short. I moved the wiring and taped the connection to make it more waterproof.

[AirMiles]

Three years ago I had the same problem but in 100 degree Florida heat. I could not get the A/C to turn on no matter what I tried including resetting and checking connections. The next day I bought a new thermostat from Camping World. When I was going to install the new thermostat, the old one started working. I put the new thermostat in a drawer as a backup in case the old one quit again. Three years later, the new thermostat is still in the drawer. In my case, buying a new thermostat was all that was needed to fix the old thermostat.

[Spartanguy]

The new (unnecessary until I broke the other) thermostat has arrived. It is pretty, I like the black, other than that...same problem. Now on to the harder solutions and pulling my hair out.

[Spartanguy]

Confusing photo perspectives, sorry. The first photo is me pressing the inside temp with unit turned on the second photo is me pressing the temp with unit turned off and set to 65.

[Spartanguy]

Originally Posted by Dixie2019

Hey Russ - I had a similar problem last winter. The problem was not inside but outside. There was a short on the roof of my 20FB FC that was created during a rainstorm when water pooled in an impression on the roof where the wiring was exposed. When the temperature dropped the water froze creating a semi-permanent electrical short. I moved the wiring and taped the connection to make it more waterproof.

I’m afraid I have a problem like this, thanks Dixie. Appreciate your input, this is the next suggestion to troubleshoot as the change of thermostat didn’t fix it.

[Jim Flower]

Originally Posted by AirMiles

Three years ago I had the same problem but in 100 degree Florida heat. I could not get the A/C to turn on no matter what I tried including resetting and checking connections. The next day I bought a new thermostat from Camping World. When I was going to install the new thermostat, the old one started working. I put the new thermostat in a drawer as a backup in case the old one quit again. Three years later, the new thermostat is still in the drawer. In my case, buying a new thermostat was all that was needed to fix the old thermostat.

That's how I "fixed" mine with the same issue. I also sprayed some electrical wire dryer in the phone connection up in the unit on the interior roof. I also disconnected both the AC and DC power overnight. The thing worked in the morning but I think it was the threat of loosing its job. I have been lugging around the spare for 3 years as a threat. Jim