Dometic AC Cooling too much

JimOneil43 · 07-03-2018, 04:57 PM

The AC in our Forester seems to be cooling too much. We set it at 80 degrees and it seems to want to cool to about 73 degrees. I'm not sure if it is a defective thermostat or if it is a problem with the AC unit. Does anyone have any thoughts or experience with this problem? The thermostat works just great when it is controlling the furnace in a heating mode.

BandJCarm · 07-03-2018, 04:59 PM

Man. Bring it down here. I wish!

rockfordroo · 07-03-2018, 05:05 PM

It should run until the t-stat tells it not to. I suspect your T-stat.

Thurman · 07-03-2018, 05:10 PM

There have been posts on this site about this before. I remember, barely at times though, that some RV owners have removed the t'stat from the wall and found a hole for the t'stat wiring that is larger than needed. Some, including me, believe that warm (warmer than ambient air within the RV) flows up the inside of the wall and out the hole telling the t'stat that the ambient air is warmer than it really is. This leads the t'stat to tell the A/C unit to keep running even though the ambient air within the RV is cool enough. Options for a fix have been to stuff some fiberglass insulation into the hole or put tape over the hole to prevent this air flow. Good Luck

JimOneil43 · 07-04-2018, 01:35 PM

Quote:

Originally Posted by Thurman

There have been posts on this site about this before. I remember, barely at times though, that some RV owners have removed the t'stat from the wall and found a hole for the t'stat wiring that is larger than needed. Some, including me, believe that warm (warmer than ambient air within the RV) flows up the inside of the wall and out the hole telling the t'stat that the ambient air is warmer than it really is. This leads the t'stat to tell the A/C unit to keep running even though the ambient air within the RV is cool enough. Options for a fix have been to stuff some fiberglass insulation into the hole or put tape over the hole to prevent this air flow. Good Luck

Yes, I kind of suspected that it was the thermostat, but I never would have figured this one out !! I will check it out, if I can figure out how to remove the t/stat without damaging either it or the wall. Thanks a lot for the info, Thurman...I appreciate it a lot.

Thurman · 07-04-2018, 02:27 PM

Can you post a photo of the t'stat? Others on this site may have the same t'stat and can share how to remove the cover. Most t'stat covers just snap on. Try holding the cover with thumb's and index fingers of both hands, then slightly pull down while pulling the bottom out and up. Make sure to cut the power to the A/C unit before working on the t'stat. The t'stat is low voltage but I wouldn't take the chance on damaging it. When you get the cover off and then the baseplate IF you find a large hole behind the baseplate please share a photo so others will know that this could be/most likely will be a problem.

Teaman · 07-04-2018, 07:28 PM

Teaman here. .............. Had the same problem with the A/C unit in my Sunseeker 2300. I measured the temperature at the thermostat location with a laser remote reading thermometer. Found the temperature in that corner where the thermostat was mounted was reading five to eight degrees higher than the temperature in the main part of the coach.

That corner wall position is near the outside wall and also the dinette window. IMHO there is very poor ambient air circulation there. When the main coach space is cool, this corner location is still very warm. So the A/C unit keeps running trying to cool down the thermostat.

I just made a note to set the digital dial on the thermostat eight degrees warmer than what I really want the coach air to be set at. Seems to be working OK like that.

OldCoot · 07-04-2018, 07:55 PM

Quote:

Originally Posted by Teaman

Teaman here. .............. Had the same problem with the A/C unit in my Sunseeker 2300. I measured the temperature at the thermostat location with a laser remote reading thermometer. Found the temperature in that corner where the thermostat was mounted was reading five to eight degrees higher than the temperature in the main part of the coach.

That corner wall position is near the outside wall and also the dinette window. IMHO there is very poor ambient air circulation there. When the main coach space is cool, this corner location is still very warm. So the A/C unit keeps running trying to cool down the thermostat.

I just made a note to set the digital dial on the thermostat eight degrees warmer than what I really want the coach air to be set at. Seems to be working OK like that.

You can also mount a small fan to circulate the air in that corner. DW uses one on her side of the bed for her hot flashes.

AbdRahim · 07-04-2018, 08:27 PM

Quote:

Originally Posted by BandJCarm

Man. Bring it down here. I wish!

Amen. Want to trade. That is the opposite of what I hear most saying., but I guess either way is a problem. Hope you get this solved.

W5CI · 07-04-2018, 08:35 PM

Bring your RV to Arkansas, it was 97 here today and I doubt that you would be thinking that your AC cooled to much. You would be looking for a Second AC or maybe a Third.

Kirk S · 07-08-2018, 09:14 AM

Our thermostat is on the bedroom wall. If I set it on 80 the coach will stay around 75 (only if parked in the shade).The other side of the wall is the bathroom with a skylight and another skylight mid coach. If parked in the sun, even with the bathroom air conditioner vent open, the bedroom is always warmer. I found that aiming a bedroom vent toward that corner helps the thermostat setting accuracy. Otherwise it's 5 to 7 degrees off setting. Setting the stat higher, like Teaman suggested works better.

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