Dometic A/C issue

KDHfan · 08-31-2016, 07:30 PM

Camping over the weekend and had an issue with our Dometic A/C unit. Temps were in the mid 90's, no clouds. We were parked in full sun... So needless to say, it was hot.
We had the a/c running with the fan on continuous "Hi" for a while to get the inside temp down to where we wanted it. I then switched it over to "auto" so that it would shut off when it reached desired temperature.
The problem: When the desired temp was reached, the fan would shut off (because it's on auto), but the compressor continued to run. It would run for about 3-seconds, then the fan would kick back on. I tried everything on the thermostat, but nothing would fix it. Finally, after the sun went down, it started working properly. It did this on two consecutive days.
Anyone know what would cause this?
Coachmen Apex 288BHS. 13,5k AC.

danny296 · 08-31-2016, 07:41 PM

Yep we did,on a brand new unit,I had service come and look at it,they replaced control panel and thermostat . It worked for a few weeks with no problems,then same old stuff, they don't know what the problem is, still working on a fix..

Bluepill · 08-31-2016, 07:43 PM

It *may* be "normal" operation. My 10K BTU Dometic "CoolCat" heatpump/AC often does the same thing. My best guess is that the fan shut down period is used to give the thermostat a chance to detect temperature with no air moving around it. The cycle will repeat from time to time, and eventually the fan speed will switch back to low rather than high. This is usually in the evening when the heat load is becoming less.

It's also possible that it is a microprocessor program fault. My unit is past warranty, so I am not going to bother with it, since the overall operation is fine.

You can reboot the thermostat microprocessor by disconnecting the 12 volt battery for 15 minutes when you have no shore power connected.

**Bama Rambler** · 09-01-2016, 10:19 AM

Mine did it once, but hasn't done it again. There have been reports of it happening because the wall behind the thermostat wasn't insulated and it allowed hot air to continually trigger the t-stat after the fan shut down. Insulating behind the t-stat and/or adding some type stand-off mount to it seemed to fix the problem.

I assume you also have the LCD thermostat. If so, you can initialize it and see if that helps.

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