Domestic AC Issue

[Jim_Hull]

Dometic AC Issue

I am having an issue with the front AC unit on my Big Country 4010. It is cooling fine, but it is running for a while then kicking off and almost immediately, within 10 seconds, kicking back on and running for another full cycle then doing it all again. Our front unit has been replaced twice under warranty for issues with freezing up and leaking water into the coach or just not cooling. This one is cooling, just cycling way too often. The rear unit runs rarely because the front unit is running so much it is cooling the rear a lot as well. Any idea what my issue is? Do I have a control board going or gone bad? Other ideas? Thanks in advance for any suggestions or help.

 

[wdk450]

Re: Dometic AC Issue

I am having an issue with the front AC unit on my Big Country 4010. It is cooling fine, but it is running for a while then kicking off and almost immediately, within 10 seconds, kicking back on and running for another full cycle then doing it all again. Our front unit has been replaced twice under warranty for issues with freezing up and leaking water into the coach or just not cooling. This one is cooling, just cycling way too often. The rear unit runs rarely because the front unit is running so much it is cooling the rear a lot as well. Any idea what my issue is? Do I have a control board going or gone bad? Other ideas? Thanks in advance for any suggestions or help.

The AC component that is MADE to cut the compressor while the blower is still running in AC mode is the freeze sensor. For my unit this is a hockey puck shaped device in a formed stiff wire holder that is clipped into a cooling tube. In any case it is a sensor device attached to the cooling evaporator with a pair of wires going to the control box. If ice forms in your evaporator from condensation water, the airflow is blocked, and the compressor can stall out, tripping your AC circuit breaker.

So maybe you have a problem with the freeze sensor, its operation (it is a thermal switch that should be OPEN when it senses over 42 degrees - closed 42 degrees and under) could be faulty. Also check for "short circuit" paths between the intake and output airflow sections which can be often found in the intake walls above the air filter. Gaps can be sealed up with duct tape.

Last of all, with the limited insulation in RV's these units struggle to keep up. Then they can't cool the trailer much into the 60 degree range as the evaporator starts freezing up. With 75 degree temperatures in my trailer, the air coming out of the air ducts is 49 degrees. I think that is pretty good for a 10 year old unit I have been fulltiming in for over 2 years.

Good Luck!!!

On edit: Here is an old post of mine from 2009 with a link to a Duo Therm SERVICE manual. See OTHER PROBLEMS (P. 62?) of the manual for tips.

"Gang:
I found the Duo-Therm Service manual here:
http://bryantrv.com/docs2/docs/acservice.pdf

BTW this Bryant RV site is a treasure trove of other RV appliance manuals. "

 

[Jim_Hull]

Re: Dometic AC Issue

The AC component that is MADE to cut the compressor while the blower is still running in AC mode is the freeze sensor. For my unit this is a hockey puck shaped device in a formed stiff wire holder that is clipped into a cooling tube. In any case it is a sensor device attached to the cooling evaporator with a pair of wires going to the control box. If ice forms in your evaporator from condensation water, the airflow is blocked, and the compressor can stall out, tripping your AC circuit breaker.

So maybe you have a problem with the freeze sensor, its operation (it is a thermal switch that should be OPEN when it senses over 42 degrees - closed 42 degrees and under) could be faulty. Also check for "short circuit" paths between the intake and output airflow sections which can be often found in the intake walls above the air filter. Gaps can be sealed up with duct tape.

Last of all, with the limited insulation in RV's these units struggle to keep up. Then they can't cool the trailer much into the 60 degree range as the evaporator starts freezing up. With 75 degree temperatures in my trailer, the air coming out of the air ducts is 49 degrees. I think that is pretty good for a 10 year old unit I have been fulltiming in for over 2 years.

Good Luck!!!

On edit: Here is an old post of mine from 2009 with a link to a Duo Therm SERVICE manual. See OTHER PROBLEMS (P. 62?) of the manual for tips.

"Gang:
I found the Duo-Therm Service manual here:
http://bryantrv.com/docs2/docs/acservice.pdf

BTW this Bryant RV site is a treasure trove of other RV appliance manuals. "

Bill,

Thanks for the info. I will look in to this info and see if any of this might be the problem. I noticed last evening as the coach cooled down and the unit caught up that the unit did less of this. Maybe it was just struggling to keep up. Also, the thermostat was set on 68 degrees, so we were really trying to cool it down from an interior temp of 82 degrees.

 

[Lou_and_Bette]

When I have mine set on "auto," as the temperature in the rig approaches the temperature setting on the thermostat, the AC will seem to pause for a short time then, come back at a higher/lower fan setting and repeats this "decision making" often. If this annoys me, I will change the thermostat a couple of degrees and this " cycling" usually stops.

 

[Thunderbolt]

I have the same problem with the three A/C units in our 2018 Cyclone 4005. All three of them will run for awhile, then start the off/on cycling sometimes for an hour. According to the infrared thermometer the temperature at the thermostats are no where near the set temperature. Last Saturday night, we started the A/C in the bedroom after shutting down the garage A/C. The living room was set to 72 degrees as was the one in the bedroom. Both units were cycling off for a few seconds, then immediately back on. I have no idea how long this lasted as I fell asleep. During the night the bedroom A/C would cycle on and off as intended. The living room had cycled off at 72 degrees and during the night the bedroom was supplying enough cold air to keep the living room A/C from cycling. In the morning when we shut off the bedroom A/C and used only the living room A/C, it would cycle off and on for about an hour then run normally. Fan speed was set on AUTO and the thermostat was set to 72 degrees. The garage A/C does the same time. Somewhere, I don't remember where, there was a post that a certain board was going bad and needed replacement. Anyone know about this?