Dometic 5 Button Thermostat Lost One Zone

I just wanted to chip in and agree with the above posters in thanking Doug for all his help. We had an a/c unit problem a couple years ago and his help was most valuable in installing the new one and getting everything up and running.

I just wish he was operating near my home so I could just bring the RV to him and my husband didn't have to do the hands on work. We have not had good experience having to pay high rates for someone to learn by trial and error on our coach.

THANK YOU DOUGRAINER!

found the broken part above control box. Spliced back together and everything works. Thanks Doug for pressing me to go back and check again. Your information was extremely important and I thank you for that. Guys like you helping the uninformed like me are extremely rare anymore so take a bow you deserve it.

Excellent diagnostic job, Doug. Thanks again for your professional assistance.

ok I found the problem on the phone cable. cable laid over a sharp edge on control box on zone 2 unit and wore through. If it is possible to repair there is enough length to still plug in.

It is NOT the tstat. The problem is between the 2 AC units. That cable is either cut/chewed or there is corrosion you did not see. Doug

Hi Doug, First thanks for the info. My RV is a 5th wheel Montana 3615 RE I checked the phone cable. The rear air conditioner has 2 cables and the front has one. The way it started was last week my wife came to me and was worried that the digital display didn't show zone 1. I turned off thermostat and turned on and there it was. You couldn't set temp just showed fan auto and cool and temp. I did the reset this week by holding mode and zone till ff showed then released now the thermostat only shows zone 2 rear. I used your idea and checked zone 2 and sure enough there was 2 phone type cables plugged in. I removed and reinserted several times. They didn't look corroded. I then went to zone 1 and did the same thing to the one cable there. Did not help. Reset thermostat but still does not show zone 1. If it means anything besides a 10 cent cup of coffee but I worked for 35 years in electronic/mechanical repair. Some on e said there was a problem with cold solder joints on this thermostat but could be anything. Any ideas you have would be greatly appreciated. Don't know if they are penquins

Go to the Zone 1 control board and unplug the phone type modular plug. Look at the plug and see if it is corroded. The NORMAL wire flow on the phone type cable is----The tstat phone cable goes to the front AC (Zone 1). Then the Front AC has a phone type cable that goes direct to the rear AC (Zone 2). But the tstat Phone type cable CAN come from the Zone 2 control board. It is just most OEM's run it from Zone 1. IF you do NOT see Zone 1 but Zone 2 operates, it is possible that the tstat cable goes to Zone 2 first and then to Zone 1. IF the cable between Zone 1 and Zone 2 is corroded or cut/chewed, you will not see Zone 1 on the wall tstat. Are the roof units low profile Penguins? What year model is the RV? Doug

The thermostat communicates with the units using what looks like a phone line. Go to the Zone one unit open the bottom panel and find the phone connector and unplug it and plug it back in. Do the same at the thermostat end. Can't guarantee anything but it fixed mine.