Dometic AC/HEAT pump not working

[Jenny cantrell]

Hi All,

We just received our 2021 Georgetown GT7 from forest river and on our first voyage we were trying to test things out, the AC/Heat Pump doesn’t seem to power on. If I put it in Fan mode I can get the fan to turn on and then it shuts off. Any ideas what to check? Seems odd both are doing the same thing and both are the same units I believe. This is controlled through a touch screen precision circuits touch panel. Checked the breaker and flipped it off and back on, but that didn’t help.

Thank you in advance!

[Scrapper]

Welcome to the forum from Wisconsin.
How cold is it where you are? Heat pumps do not work below 40 - 45 degrees.

[Jenny cantrell]

Thanks for the reply, we did try just the fan and it runs for a few seconds and it kicks off. Then we tried the AC to see if we could get that to kick on, that also didn’t work, along with the heat pump we tried and it didn’t even kick on, does temperature impact the ability for the unit to even kick on at all? I just assumed it would run but wouldn’t be efficient due to the 32 degree temp. I also would think if I set just the fan to high it would work? Thanks again for any help here.

[Scrapper]

I believe the heat pump samples the outside air for temperature, how I'm not sure. Temperature does impact the units ability to run. The operation depends on the principal of how heat changes liquids to gas then cooling changes that gas back to a liquid. There needs to be enough heat in the outside air to convert the liquid to gas and the inside air needs to be cool enough to convert it back to liquid. If the unit was allowed to continue to operate with cold outdoor temperatures it will freeze up causing damage to the compressor.

When the unit is used to cool the inside of your rv the process is reversed. The direction of the flow from liquid to gas then back to liquid is accomplished by valves in the unit.

If your interested more info on how it works can be found in the following links.

https://www.newair.com/blogs/learn/c...an-be-a-heater
https://www.carrier.com/residential/...eat-pump-work/

[anaviator]

Originally Posted by Jenny cantrell

Thanks for the reply, we did try just the fan and it runs for a few seconds and it kicks off. Then we tried the AC to see if we could get that to kick on, that also didn’t work, along with the heat pump we tried and it didn’t even kick on, does temperature impact the ability for the unit to even kick on at all? I just assumed it would run but wouldn’t be efficient due to the 32 degree temp. I also would think if I set just the fan to high it would work? Thanks again for any help here.

Welcome to the forum. We have a 2020 Berkshire with the same Precision Plex system. If the oustide temp drops below around 40 degrees (haven't been able to determine exactly what the cut off is), any A/C units with heat pumps installed will not run in any mode, including just fan. You should see "Heat Pump Lockout", or something similiar to that, on the LCD panel when the lockout is active. I confirmed this with the Precision Plex folks when our bedroom unit started shutting off in the middle of the night (we usually leave the fan on for white noise).

The Berky has an external temp sensor that trips the lock out for the heat pumps. If your unit doesn't have the external temp sensor, the A/C units will activate momentarily to pull air across the internal temp sensor and determine if the temp is too low to operate - that's likely why yours run for a few seconds and then shuts down.

While I understand the reason for locking out the compressors below a certain temp, the fan lockout is annoying. I prefer to have the air circulation and white noise at night.

[Andystoys]

I realize this is an older topic but thought I'd chime in incase someone is looking for information. The manuals that came with my 2021 GT7 state the Dometic heat pumps will not work below 45 degrees. This has been true to almost the exact temp in my case. I have also found that once they stop working I can't turn the fan on either. I have found that if I reset the battery disconnect I can then turn on the fan and it will stay on all night.

Robert & Debbie
2021 GT7 36D7
2016 Cherokee Trailhawk

[Bfmcbride]

Sorry that I am late to the party, here. I had the same issue, found this thread, and still could not restart the unit. Our local Dometic service center refused us service becauae despite being two years old, it is installed on a 1972 refurbished Airstream.

I cleaned the airfilter. I saw the RJ11 cable running from the thermostat going into a female to femal RJ11 jack. There was "orange- colored" staining on outside of this piece. I wiggled loose the RJ cable from.the connector and found copper corrosion on the copper pins on the RJ11 connector. Picked it off with a wire brush and reconnected it. Reset the thermostat and the HP magically reappeared.

So, if you vacation close to salt water or any very humid environment, check this $4 part. Then, wrap electrical tape to seal it from the environment.