Dometic thermostat malfunction.

[peaeye1]

This is on a Winnebago 5th wheel.This thermostat can be set to one, two or both ac's.Both units work fine,fan,compressor, but the inside temp setting on the thermostat for the 2nd ac is now starting to read down in the 40's and 50's at times.As a result I cannot get the 2'nd ac to come on.At random times it will show in the 80's.I know where the sensor is for the 2nd ac, and have made sure no dust etc was on it. It has worked fine for several months until today. Any thoughts?

[peaeye1]

bgum wrote:
What was the problem and what did it take to fix it?

I will have to get a rv tech in AZ to take a look next month, when we get there. The temps in NM have not required a ac in the last few weeks. I will post when I find out.

[bgum]

What was the problem and what did it take to fix it?

[bgum]

There are two one inside one outside. The most likely one to be corroded is the outside. On mine it was the connector on the communication wire inside. There was a little bit green corrosion on both the wire end and the connector end. I cleaned both and after a couple resets of thermostat problem was solved. It doesn't take much to cause a problem.

[peaeye1]

bgum wrote:
There is a box inside in the overhead unit. Follow the communication cable(telephone wire) from the thermostat to the board. There is also a box with a board on top with the unit. Mine was on the front passenger side of the unit. If there is any cable connectors clean both the cable end and the connector. You can find instructions online by searching. Good luck

I had the filter cover off and did not see a box or board. The main cover on the inside has sealant on the edges where it contacts the ceiling . Could the box or board possibly be accessed if I removed the whole inside cover.I have no problem doing this if it will get me where i want to be.Did you say the connections could possibly be reached by removing the outside cover? I have been researching the cleaning methods.

[bgum]

There is a box inside in the overhead unit. Follow the communication cable(telephone wire) from the thermostat to the board. There is also a box with a board on top with the unit. Mine was on the front passenger side of the unit. If there is any cable connectors clean both the cable end and the connector. You can find instructions online by searching. Good luck

[peaeye1]

camperguy99 wrote:
On my 2015 Tuscany the thermostat sensor wasn't even connected! Works a lot better after the wires were attached by myself!

I believe mine are connected, as it worked fine up until last week.

[camperguy99]

On my 2015 Tuscany the thermostat sensor wasn't even connected! Works a lot better after the wires were attached by myself!

[peaeye1]

bgum wrote:
clean contacts. You are experiencing communication problems between the boards in the AC and thermostat.

I have done many repairs and adjustments on a few rvs, but never cleaned contacts. Please, a little more guidance if you can. Where is the board located? Is it in the ceiling unit and how do I access it.

Thanks

[bgum]

clean contacts. You are experiencing communication problems between the boards in the AC and thermostat.

[peaeye1]

more update.....after reset ac will keep cycling, with the compressor coming on and running for about about a minute, shuts down and starts back up, inside temp shows 71 after reset.

Bad board, bad ther, ac going bad ???

[peaeye1]

update ..........got the manual out and said to do a reset on the ther.The inside now reads "somewhat" better,not ridiculous low temps, but it is not cycling right. I will see more tomorrow if we have to use the ac.

[bgum]

Could be bad thermostat but at $130 per copy be sure. You can't return electronic items. Clean all contacts where the communication wire runs to. Both where the plug plugs into and on the boards in the AC unit.

[Hunter11]

We had this same issue on our bedroom AC unit when we went to do the PDI on our trailer. Inside temp was reading way low and the AC would not function correctly. It turned out to be a defective thermister (temp sensor) on the bedroom AC unit. Our thermostat controls both zones and the living room was functioning fine. They replaced the thermostat first and that did not fix it. They replaced the wire from the AC down to where the sensor mounts and that did the trick.

[peaeye1]

A little update, after fooling with the sensor and watching the inside temp reading, i think its just a thermostat gone bad, The inside temp will all of a sudden read in the high 70's, ac will come on, inside temp on the thermostat will drop to 40's in a few seconds, ac will turn off in the auto mode and thermostat will then show 70's again and go thru the cycle again. I even pulled the wire out of the wall a little way,s and covered the sensor with a heavy piece of cloth. Bad thermostat or what?