Dometic AC unit

[brnthumbinfl]

We purchased our 2019 Mesa Ridge 21RBS TT from Lazy Days in Tampa, January 2019. We've had it in twice for warranty repairs. Both times, we reported the AC unit would hover when it reached the set temperature. Particular at night, the unit will cycle on for as little as 10 seconds then cycle off for 10 seconds. Back and forth as many as a dozen times. The unit is not terrible quiet, so this gets irritating when you're trying to sleep. Plus it can't be good for the unit.

Lazy Days checked it twice without finding anything wrong. Of course it was winter when the unit isn't really working. They tried insulating the thermostat, then I forced them to replace the thermostat. Neither action corrected the problem. Currently I am beginning to think it may be the unit itself. It seems when it goes into hover mode, I'm not sure its really cooling as the air seems just room temp.

Any ideas?

Brnthumb

[TomG2]

ajriding wrote:
TomG2. Now that you have tried all the above suggestions, just let us know you have, and then we will offer the real answer. There can be only one answer. No one has ever had an issue and solved it by other means.

Problem solved. New trailer has Coleman Mach AC. No problems. No "false starts". No short cycling. You can keep your secret answer.

[CavemanCharlie]

philh wrote:
ok, the pointy copper thingy.

On my unit it was tucked in behind the air flow. I moved it into the airflow and my short cycling went away. I froze my wife out, it was working that much better. Such a simple fix.

I like this name the best.

I've had to do the same thing on a Window Air Conditioner once.

[ajriding]

thermocouple
agree. I didnt want to disagree.
The thermometer is still the copper wire that is flexible and should sit in the flow of return air. If this is tucked away, or touching something with a different temp then issue arise. Easy to check this by taking ceiling assembly off (maybe just the air filter screen) and bending it into position. -easy to do, and always start with the easy suggestions first...

[philh]

ok, the pointy copper thingy.

On my unit it was tucked in behind the air flow. I moved it into the airflow and my short cycling went away. I froze my wife out, it was working that much better. Such a simple fix.

[smthbros]

A thermocouple is a device which generates electricity when subjected to a flame, most often from a pilot light.It is unlikely to be found on an rv air conditioner.
The device mentioned in previous posts would likely be a thermister, which is a resistor whose resistance varies with the temperature it is subjected to. This may be found lodged into the evaporator coil of the air conditioner. Its purpose is to turn off the compressor when the condensation on the evaporator begins to freeze.

[TomG2]

ajriding wrote:
Thermocouple is the bare copper wire (tube) with the big end (about pencil thickness) and is a thermometer for the AC to measure incoming air. .

y

Why not call it a thermometer? Thermocouples are usually used as safety devices to control gas flow.

I have tried all the suggestions and many more.

[ajriding]

Thermocouple is the bare copper wire (tube) with the big end (about pencil thickness) and is a thermometer for the AC to measure incoming air. Just to clarify if any readers wonder.

If you have issues and want to fix, then really try the suggestions. There will be no real answer, that was kidding, all answers are possible to be your issue or not. If you do not try to solve, then it wont fix itself.

Even professional auto mechanics try suggestions. They start with the easy thing, charge you, then move on to more and more complex and expensive things to see if it will work, all the while charging you for their attempts. If you can do it yourself for free then saves money. Process of elimination. You have to try the fixes known to cause issues.

[TomG2]

ajriding wrote:
TomG2. Now that you have tried all the above suggestions, just let us know you have, and then we will offer the real answer. There can be only one answer. No one has everss had an issue and solved it by other means.

Thanks, but I am not the OP, just following. This is the third AC unit to do this for me, so I am curious. For now, I simply turn it off in the early morning hours. As far as trying all the suggestions, I will leave that to others. I did not even know that Air Conditioners had a "Thermocouple".

If you have the "Real" answer, many would be glad to hear it.

[ajriding]

TomG2. Now that you have tried all the above suggestions, just let us know you have, and then we will offer the real answer. There can be only one answer. No one has ever had an issue and solved it by other means.

[TomG2]

Hoping someone comes on with the real answer. Mine does the same thing when the temperature outside is only a few degrees warmer than inside. I suspect it is some kind of "feature" that is supposed to keep the AC from freezing up or hurting itself. Any technicians out there?

[beemerphile1]

Mine has done similar when fan is on auto. Set to either low or high.

[philh]

Where is the thermocouple? Pull the panel off, and make sure the thermocouple is in the air flow. I bent mine about 30 deg forward into the airflow and it works perfectly now.

[DarkSkySeeker]

brnthumbinfl wrote:
...the unit will cycle on for as little as 10 seconds then cycle off for 10 seconds. Back and forth...

Perhaps it is the differential temperature setting - see LINK

[Guy_Roan]

brnthumbinfl wrote:
We purchased our 2019 Mesa Ridge 21RBS TT from Lazy Days in Tampa, January 2019. We've had it in twice for warranty repairs. Both times, we reported the AC unit would hover when it reached the set temperature. Particular at night, the unit will cycle on for as little as 10 seconds then cycle off for 10 seconds. Back and forth as many as a dozen times. The unit is not terrible quiet, so this gets irritating when you're trying to sleep. Plus it can't be good for the unit.

Lazy Days checked it twice without finding anything wrong. Of course it was winter when the unit isn't really working. They tried insulating the thermostat, then I forced them to replace the thermostat. Neither action corrected the problem. Currently I am beginning to think it may be the unit itself. It seems when it goes into hover mode, I'm not sure its really cooling as the air seems just room temp.

Any ideas?

Brnthumb

Are you sure it is doing it a "dozen times"
If you read your manual, you'll find out that it is normal and is adjusting itself to a lower speed once it reaches the set point.

Guy