New Dometic 3 button thermostat shuts down AC system at will

Domestic had a bunch of bad control boards a few years ago. We just had the thermostat and control board replaced on our digital control 15K a/c system and it solved a few screwy problems. Temperature control is still terrible. Stat is very slow to react. You cannot change to any other stat without rewire of the control because this one uses only 3 wires including furnace control. The switching between low and high fan uses control signals on one wire which causes the pause between fan speeds. Low on our 15K doesn't seem to have much cooling capacity and you only get high when there is 4 to 5 degrees from set point. We end up forcing the fan to continuous high and letting the compressor cycle to get compfortable. Seems like a junk design to me--probably saved someone a $1.95. My son just got a Coachman TT with a Coleman a/c and a manual mechanical thermostat. Kind of wish I had the same!

Vulcan Rider wrote:

RobertL0 wrote:

When in AC mode, (fan speed set to low or high), the RV will get to it's set point, then the compressor AND the fan will shut down at the same time.

For me to restart the cooling, I need to shut off the AC via the thermostat, and then turn it back on.

Sounds like normal operation to me. If the fan runs all the time, your humidity control will be VERY poor.

This is how my house and RV work.....and even some window A/C units too......except for the restarting part, that is.

Are you SURE that turning the temp down 5 degrees or so will not cause it to restart ? (Some will not restart within 5 minutes.)
It is possible that your stat just has too wide a range to keep things comfortable.

If set on Lo Med or Hi fan speed and set for cooling that means the FAN will run continuously on RV units. In MY house, if I set the fan to AUTO the whole house fan turns OFF with the compressor. If I set the Fan to ON, then it will run continuously regardless of compressor on or OFF. Doug

Thanks

Things have been working well for the last 2 months. This problem just started, maybe a got a surge from a campground that did something to the thermostat or upper board...

TXiceman wrote:
One thing to check is the power source for the thermostat. It should be fed from a separately fused circuit....ie, nothing else on this circuit. The newer thermostats are prone to interference fed through the power source.

Ken

One thing to check is the power source for the thermostat. It should be fed from a separately fused circuit....ie, nothing else on this circuit. The newer thermostats are prone to interference fed through the power source.

Ken

OK, thanks Doug. I'll replace the thermostat first and see how we do

Thanks again

dougrainer wrote:
ONLY the single zone tstat will work with your AC control board. So, no, you cannot install another brand/type tstat. It is either the wall tstat or the upper control board. You purchase the part and install and Dometic will not warranty it. You must go to a service center for warranty work. But, a tstat is cheaper than taking it in and wasting your fuel and time. IF the tstat does not fix the problem, then the upper board is at fault and you can then tell the service center that you have determined the upper board is bad. IMO, the upper board is bad. Doug

I believe when you set the fan to low or high, it should run ALL the time, whether or not you have the AC or heat pump working..

Vulcan Rider wrote:

RobertL0 wrote:

When in AC mode, (fan speed set to low or high), the RV will get to it's set point, then the compressor AND the fan will shut down at the same time.

For me to restart the cooling, I need to shut off the AC via the thermostat, and then turn it back on.

Sounds like normal operation to me. If the fan runs all the time, your humidity control will be VERY poor.

This is how my house and RV work.....and even some window A/C units too......except for the restarting part, that is.

Are you SURE that turning the temp down 5 degrees or so will not cause it to restart ? (Some will not restart within 5 minutes.)
It is possible that your stat just has too wide a range to keep things comfortable.

RobertL0 wrote:

When in AC mode, (fan speed set to low or high), the RV will get to it's set point, then the compressor AND the fan will shut down at the same time.

For me to restart the cooling, I need to shut off the AC via the thermostat, and then turn it back on.

Sounds like normal operation to me. If the fan runs all the time, your humidity control will be VERY poor.

This is how my house and RV work.....and even some window A/C units too......except for the restarting part, that is.

Are you SURE that turning the temp down 5 degrees or so will not cause it to restart ? (Some will not restart within 5 minutes.)
It is possible that your stat just has too wide a range to keep things comfortable.

ONLY the single zone tstat will work with your AC control board. So, no, you cannot install another brand/type tstat. It is either the wall tstat or the upper control board. You purchase the part and install and Dometic will not warranty it. You must go to a service center for warranty work. But, a tstat is cheaper than taking it in and wasting your fuel and time. IF the tstat does not fix the problem, then the upper board is at fault and you can then tell the service center that you have determined the upper board is bad. IMO, the upper board is bad. Doug

No I haven't. I'll try that today and run it...Thanks

newman fulltimer wrote:
have you tried resetting it?Fan on auto turn off and push the power and plus button at the same time two lines will appear the stat isnow reset

have you tried resetting it?Fan on auto turn off and push the power and plus button at the same time two lines will appear the stat isnow reset