Air Conditioning Issue

[jmarnell]

We have a 2018 Cyclone 4005 that has had an intermittent issue with the main central air conditioner. It's a Dometic Brisk II. It will work fine, but then sometimes after reaching the set temperature and cycling off it won't restart. The temperature inside will get several degrees hotter, but no go. I've tried lowering the temp on the thermostat and it still won't run. But if I turn off the system at the thermostat, let it sit for a few seconds, and then turn the system back on, the air conditioner kicks right in and works fine again. The dealership thought it was icing up because the diverter plate had slipped out of place, but that didn't help. I then thought the thermostat might be bad, so I ordered and installed a new one. But the problem continues. We took the rig out last week for 4 days, and everything worked great for 2 days, but then on the 3rd day the problem struck again. The AC cycled off and would not restart until I turned it off at the thermostat and then back on. Any ideas? Could it be a control board problem? Intermittent electrical issues are so hard to diagnose!

 

[danemayer]

If you have the Precision Circuits energy management system, with a small display near your other controls, it's possible it could be the problem. If you have three A/C units running, along with electric water heater, microwave, etc., you could be pulling too much power and the PCS is cutting power to selected appliances.

My understanding is that when the PCS cuts power to the A/C unit, it does so by simulating a freeze-up; the compressor shuts off, but the fan continues to run. If that's your symptom, and you're running a lot of appliances concurrently, it could be normal operation. If that's the symptom, and you're not running a lot of appliances, it could be a loose wire.

Pages 14-16 of our owner-written Electrical User Guide provide additional information and pictures.

 

[jmarnell]

If you have the Precision Circuits energy management system, with a small display near your other controls, it's possible it could be the problem. If you have three A/C units running, along with electric water heater, microwave, etc., you could be pulling too much power and the PCS is cutting power to selected appliances.

My understanding is that when the PCS cuts power to the A/C unit, it does so by simulating a freeze-up; the compressor shuts off, but the fan continues to run. If that's your symptom, and you're running a lot of appliances concurrently, it could be normal operation. If that's the symptom, and you're not running a lot of appliances, it could be a loose wire.

Pages 14-16 of our owner-written Electrical User Guide provide additional information and pictures.

Thanks, Dan, but while we have the PCS I don't think that's the problem. From what I read, the central main unit is supposed to always run, with the PCS shedding power between the front and rear AC units (we have 3 units). Also, as I noted in your comment, the PCS would have the compressor go off but the fan continue to run. I've noticed that on a hot day with the front and rear units where the fan continues but I can tell the compressor has shut off. In my case, the entire unit is shutting down fan and all. But good point about a loose wire. I'll have to check and make sure all the connections are tight.

 

[jmarnell]

Called out our mobile RV repair service. The problem was diagnosed as a bad relay in the air conditioning control box. Luckily he had a new one in the truck so he replaced it, and also fixed up some of the original wire connections he didn't like the look of. Hopefully we are good to go now.

 

[Dan50]

What exactly does the relay look like. I might have the same problem.

 

[jmarnell]

What exactly does the relay look like. I might have the same problem.

The relays are inside a grey control box about 5 inches square. You have to remove the air conditioning cover in your ceiling to get at it. Sorry I did not think to take a picture of it. The tech just replaced the entire control box, not just one relay (I think there were 2 or 3 relays in there). He charged me $50 for the control box.

 

[Dan50]

Thank you.