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Randall, RVIA Certification
Category: RV
Satisfied Customers: 11298
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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My Dometic AC unit shuts off in the afternoon reason (not at

Customer Question

My Dometic AC unit shuts off in the afternoon for no reason (not at temperature set on the thermostat). When I turn the thermostat to off and then back on it comes back on. This happens everyday and sometimes multiple times a day.
Submitted: 1 year ago.
Category: RV
Expert:  Randall replied 1 year ago.

Does the thermostat have any error code showing when this happens? Did you check the incoming AC voltage to see what it was? That would be a good idea here. Did you install this thermostat or is it the OEM model that came in the trailer? Get back to me with this information and I can help you sort this out. All follow ups are included in our fee

Customer: replied 1 year ago.
There is no error code on the thermostat just the temp setting. The thermostat is the original, nothing has been changed, it is a digital Dometic single zone thermostat. Here in Florida the AC runs (or needs to) almost all day/afternoon and always has.I have not checked AC voltage, where would I check that?
Expert:  Randall replied 1 year ago.

You would use a digital multimeter like you can find at most hardware stores for about $20 or so. But, if this comes right back on again with no error codes, then I suspect it may have a bad connection. If a wire is loose, it might do this for any number of times. OR it can be the thermostat or ceiling box has a bad board or one going bad. Erratic performance without an error code is one of the hardest things to track down. A new kit is about $89. The connections are going to be probably crimped wire nuts on the wall side and the ceiling box. That is accessed from under the ceiling grill once you remove it. Give those a try and see if you can see anything suspect. Let me know what you find and we can go from there.

Customer: replied 1 year ago.
I just checked with a multimeter inside the gray control box at the AC connector. There was 117 V at that point, and this was during the "first shutdown" today. Then again I turned the thermostat to off waited a few seconds til green light was out, and turned back to cool mode. It started right up
Expert:  Randall replied 1 year ago.

What was the green light?

Customer: replied 1 year ago.
The mode indicator light on the thermostat
Expert:  Randall replied 1 year ago.

O.K............just checking. Did all the connections at BOTH the thermostat and ceiling box seem tight? IF SO, then I suspect that this is a problem in either the thermostat board or the ceiling control board or relay. The safest thing would be to buy the kit. The part number is ***** the ceiling box. If the A/C is not a heat pump version, let me know and I can supply a part number.

Customer: replied 1 year ago.
All the connections at both ends seem fine. There is no heat pump, just the standard AC along with a Suburban ( (Propane)Furnace. Is the part # (###) ###-####000 ?
Expert:  Randall replied 1 year ago.

Yes...........that is the correct kit you need. Easy to install. Keep the old parts or perhaps just change out the thermostat first and see if that corrects this and you have a new spare control box. Please let me know what happens.

Expert:  Randall replied 1 year ago.

Just checking back in to see if you were able to resolve this or do we need to dig deeper into the problem? Have a safe New Year's!