Dometic A/C glitch

I would try rebooting it- turn the system off, press and hold +, press and hold on/off mode for 3 seconds. Screen should read -- , release. Press On/Off to turn off.
Should be back at factory settings.

sounds like the unit froze up and you need to do what Chris suggest.Also don't run the unit on low fan

I have the Dometic and single zone LCD t-stat also...I have experience the same thing with my Bedroom AC fan on Low over night, running fan on HI I've had no issues.

I don't know if the freeze sensor shuts it off or what, but on high it doesn't experience this issues...Dometic needs to improve this thermostat....it has other issues also, such as the fan switching from hi to lo and back to high as you initially cool the RV in Auto mode...this can also be fixed by using HI until the temp set point is reached.

Beaubeau -

My camper is in the shop right now for a very similar problem. The tech has diagnosed the problem as a bad thermostat and it is waiting for a replacement from Dometic.

My symptoms are: the AC (comp and fan) will run until the setpoint of the thermostat is satisfied and then cycles off. But it will never cycle back on even though the temp in the camper goes higher. I usually run it in AU mode and the step-down through the LO fan speed happens as it should at +4 degrees. I think if I have it in the LO mode, only the compressor is affected. The only way I can get mine to cycle back on is to turn the thermostat to the OFF setting, wait a few seconds, then turn it back on to any one of the AC settings (LO, HI or AU).

Like I said, the repair tech thinks it is a bad thermostat, BUT - I don't know if he is aware of the reset that Chris Bryant described. The tech never mentioned that and I don't think he tried it. So, when you try Chris' suggestion, please post the results here - I may need to get this info back to my tech.

Thanx

Hiking Hunter wrote:
Beaubeau -



Like I said, the repair tech thinks it is a bad thermostat, BUT - I don't know if he is aware of the reset that Chris Bryant described. The tech never mentioned that and I don't think he tried it. So, when you try Chris' suggestion, please post the results here - I may need to get this info back to my tech.

Thanx

I tried the reset before....no change...I think it is a software issue in the T-stat or AC control board.

I would suspect a BAD lo speed on the fan motor(overheating the windings). But, it is easy to replace the tstat. I doubt the upper board is at fault. I doubt a reset will fix this type problem. Resets for operation problems rarely do on Dometic CCC systems. A quick test is to swap the Lo and HI fan speed wires and see if the fan fails when putting it to HI Fan(which will energize the LO speed wiring on the motor). If it fails on LO Fan(indicating the motor will not run on hi fan continuously), then you look at the upper board or the tstat. Doug

All good stuff, thanks! The thermostat is cheap enough and easy to just go ahead and replace when I get home. And I like the idea of swapping the Hi/Lo wires for while I'm on the current trip, at least for a diagnostic.

Thanks everyone!

dougrainer wrote:
I would suspect a BAD lo speed on the fan motor(overheating the windings). But, it is easy to replace the tstat. I doubt the upper board is at fault. I doubt a reset will fix this type problem. Resets for operation problems rarely do on Dometic CCC systems. A quick test is to swap the Lo and HI fan speed wires and see if the fan fails when putting it to HI Fan(which will energize the LO speed wiring on the motor). If it fails on LO Fan(indicating the motor will not run on hi fan continuously), then you look at the upper board or the tstat. Doug

So, if the fan motor is overheating on low, why woulc the compressor turn off at the same time?

Learjet wrote:

dougrainer wrote:
I would suspect a BAD lo speed on the fan motor(overheating the windings). But, it is easy to replace the tstat. I doubt the upper board is at fault. I doubt a reset will fix this type problem. Resets for operation problems rarely do on Dometic CCC systems. A quick test is to swap the Lo and HI fan speed wires and see if the fan fails when putting it to HI Fan(which will energize the LO speed wiring on the motor). If it fails on LO Fan(indicating the motor will not run on hi fan continuously), then you look at the upper board or the tstat. Doug

So, if the fan motor is overheating on low, why woulc the compressor turn off at the same time?

I did not get that from his post. What I understood was the LO Fan FAILED to stay running regardless of the compressor. He wants the fan to stay ON 24/7 which it should when set to LO instead of AUTO. IF the fan fails, the compressor WILL be killed by the overload on the Compressor. But, it will take awhile for it to overheat. Doug

Right Doug, you understand the problem correctly.
Thanks for the clarification.