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Old 10-16-2020, 12:47 AM   #1
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A/C won't shut off

My 2017 Work & Play has a Dometic thermostat for the a/c - fan - furnace. It's been running most days, but is cool enough outside at night that I don't need it.
The last couple days, when I manually press the on/off button to off, it just keeps running. I can shut it down with the breaker. Seemed good all day today, as I was able to change the temp setting, but now that I want to turn it off....no go. Any words of wisdom, way to reset it, other ideas? Hoping it's something simple before I call an RV mobile tech. Thanks.
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Old 10-16-2020, 01:59 AM   #2
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There is a significant delay when I turn the AC in my Motorhome off. Maybe a minute or so. It eventually does turn off.
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Old 10-16-2020, 04:47 AM   #3
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I think they all have this delay function,even my house unit run a few minutes before shutting down.
As for your your unit running in cooler temps, check your fan settings, sounds like your fan in in Hi or Low not Auto.
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Old 10-16-2020, 07:16 AM   #4
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Originally Posted by Homebrew View Post
I think they all have this delay function,even my house unit run a few minutes before shutting down.
As for your your unit running in cooler temps, check your fan settings, sounds like your fan in in Hi or Low not Auto.
This.
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Old 10-16-2020, 10:10 AM   #5
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Thank for all the suggestions. The thermostat is set to Auto (and re-set, just in case). The delay to shut off is normally 30 seconds to a minute, and now it is forever. Hoping it will be an issue that a new thermostat will fix....not something like a circuit board.
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Old 10-16-2020, 10:18 AM   #6
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Originally Posted by Homebrew View Post
I think they all have this delay function, even my house unit run a few minutes before shutting down.
Yes, this is to allow pressure in the compressor to bleed off. Otherwise turning it off and right back on can cause damage because the compressor will be trying to run against an already-pressurized system.

Quote:
As for your your unit running in cooler temps, check your fan settings, sounds like your fan in in Hi or Low not Auto.
Our Dometic AirCommand AC-1511 units only fully shut down when the thermostat power button is turned off.

As stupid as it sounds, Dometic does not use a thermistor (the temperature-sensing device) inside the thermostat; they put the thermistor inside the air inlet section on the roof unit.

So even if the fan is set to Auto the fan runs on Low 100% of the time to keep some air flow across the thermistor so they can measure the room temperature to decide whether to turn the A/C or heat pump on.

Even stupider, the Dometic thermostat does have a thermistor inside it, but it's only used for the non-Dometic propane furnace; just not their own products.

HTH,

Ray
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Old 10-16-2020, 01:21 PM   #7
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A/C

If we run our AC on auto and then turn on heater the next morning both the heater and AC run. If we change the fan to high or low then we can get heater to run without the AC also coming on.
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Old 10-16-2020, 02:01 PM   #8
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Check the setting

If it is on the "ON" position it will just keep on running. Maybe play with it to see if there is an "auto" position. It will shut off and on in that position.
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Old 10-18-2020, 08:46 PM   #9
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Have you tried re-initializing the thermostat? That was a cure all for some issues I and others have had...
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Old 10-18-2020, 08:52 PM   #10
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Have you tried re-initializing the thermostat? That was a cure all for some issues I and others have had...
The RV tech stopped by yesterday and took a look. He determined that the thermostat and the control box were not communicating properly (please, don't get technical, that's my version of what he said ). We tried a bunch of different things, but it always came back to not shutting off. So, when the parts come in, he'll come back and take care of things. I'll report back then.
Thanks for all the replies!
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Old 10-23-2020, 02:10 PM   #11
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Bought the 'kit', thermostat and control box on Amazon (a reseller) and it was just installed. Everything works great - and it's now digital. A little bit different thermostat but easy to read, works like it should so I'm happy!
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