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Old 06-05-2023, 06:25 AM   #1
scott802
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Help! 2018 3121RL - Dead Dometic CT Thermostat No AC

Hi all,
We recently had our roof replaced on our 3121RL. Lo and behold we took the camper out on the road for the first time and the main A/C unit is not working. The bedroom Dometic thermostat and AC is functioning as it should. However, the living area Dometic thermostat is completely dead, no response at all. I first verified all the breakers are good etc. No blown fuses and I have power to the plugs etc. I am trying to verify that I have 12v coming into the thermostat. I also climbed up on the roof removed the AC shroud but nothing seems to be obviously wrong. Is there any possibility something didn't get properly reconnected when my roof was replaced for this AC unit? If so, why would my thermostat be dead?
Any help would be MUCH appreciated! We are out on the way to Pigeon Forge TN and need both AC units working.

Thank you!

Scott
 
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Old 06-05-2023, 07:05 AM   #2
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update

Just an update - I checked the bedroom thermostat and i have 12v on it which is good. I do not have 12v coming into the main thermostat and i can see 'E1' flashing at a very low intensity now.

Any ideas, thank you!!!
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Old 06-05-2023, 09:35 AM   #3
Daryles
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You need to take the cover off the AC unit it and check the wiring. Someone probably forgot to connect it.
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Old 06-05-2023, 11:01 AM   #4
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Not sure on your model but if memory serves me correct, on the older models the 12volts to the thermostat came from 12v wiring near the control board at the air conditioner via the RJ11 cord. (flat telephone looking cord)
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Old 06-05-2023, 07:25 PM   #5
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update - fixed

Not sure if i could have figured this out myself totally, but here is what happened. Everything was fine on the roof end, connected etc. The clue was that there was no 12v power to the thermostat. There was no ground. Apparently what happened was somewhere on the roof when it was being replaced they must have put a screw through a ground wire someplace on the decking. Just speculating but with a new ground on the thermostat it started up and it's fine now.

Needless to say, I'd like to replace both of these Dometic thermostats they're really pretty awful I've seen lots of other folks on here doing the same thing.
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Old 06-06-2023, 03:51 AM   #6
Mikendebbie
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I replaced my OEM Dometic thermostats with two of theseÖa bit pricey but they work great.
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Old 06-06-2023, 04:56 AM   #7
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I replaced my original Dometic CT thermostats with the ones Mike shows above also.
Over $500 for the two of them, but all of our AC problems were resolved by the MicroAir thermostats. Best $500 we ever spent on our rig.
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Old 06-06-2023, 05:08 AM   #8
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Dometic replace

Thanks so much! Those Micro-Air Easy Touch thermostats almost look too good to be true! they look to be a very simple wire to wire hookup also. Based on everyone's recommendations here I am going to go ahead and buy one for at least the living room main thermostat that is so problematic and see how it works.

Scott
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Old 06-09-2023, 07:20 AM   #9
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Very simple to mount and hook up. They truly work great and I did not think I would care for the blue tooth App control but I was wrong...I like the fact I do not have to walk over to the thermostat to control or check things.
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Old 06-10-2023, 04:50 AM   #10
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follow up - no furnace now

Hi all,
Just a follow up. I never thought to check the furnace operation, didn't think I'd even need it this summer, but the mountains of VA get cold in the morning.
Well, when i tried to fire up the furnace this morning off the same thermostat - nothing.
I am using the heat pump instead for now, but the furnace side doesn't work at all. So usually the fan kicks on then the furnace will fire a few seconds later but in this case it's completely dead.
So I'm wondering how it's possible when the ground wire was tapped off the outlet that affected operation of the furnace heat? It seems that the only thing that the thermostat will control now is the AC on the roof - either in heat pump mode or cooling.
Not sure if anyone has had a similar issue before, but i would think the deader putting on a new roof would have nothing to do with the furnace.
Any ideas?

Thanks everyone
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Old 06-11-2023, 04:18 PM   #11
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Quote:
Originally Posted by Mikendebbie View Post
I replaced my OEM Dometic thermostats with two of theseÖa bit pricey but they work great.
Mike, question on the replacement thermostat you showed. Was your thermostat two separate controls or Zone 1 and Zone 2 on a single thermostat?
I ask since my OEM Dometic thermostat controls both Livingroom and Bedroom AC units as two Zones. The compatible replacement for mine is: Micro-Air ASY-350-X02 EasyTouch RV 350 and it reflects 2 Zone capability.
Iím just trying to ensure Iím not missing something since I canít stand the OEM Dometic thermostat we have and havenít received a response back from the seller if a single device will control 2 AC units. Thanks!
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