A/C and furnace stopped working

[JeffPax]

Backstory goes like this: Heat and a/c have been working just fine until a little while ago. Ran the a/c all day, no problems. When it got into evening, we shut it off. When it came time for bed, slid the selector to furnace and nothing happened. Tried the selector on a/c, nothing happened. Further fiddling (analog thermostat) produced this, when selector is set to "off", then either slid to heat or cool and the temperature slider is moved to the appropriate location to trigger/request the desired effect (heat or cool), the click to engage is heard, but nothing happens. If the temperature slider is then returned to a position where the request would be cancelled, the anticipated canceling click, is NOT heard, nor is any subsequent click when returned a position for request, until the selector has first been moved to "off" again, and returned to heat or cool. Please advise.

 

[Boonieman]

The furnace and A/C are two independent units on most fifth wheel campers, so for both to not run would seem to mean that the problem is something in common with both. You said you tried the air conditioner and it wouldn't run either, but just asking, did you lower the thermostat enough to kick it on? If so, the 120volt power is in common with both those items, as well as the thermostat. But you said you could hear a relay somewhere when operating the thermostat, so first thing I would check is if you actually have 120 volts to the RV by trying to operate the microwave or some other 120 volt appliance. If no 120, then check either from the pole, surge protector not tripped, breaker inside, etc. Good luck to you.

 

[John From Detroit]

Generally furnace is a 12 volt device. A/C is 120 volt but the one thing they both have in common is the Thermostat, which is also a 12 volt device.

Suspects are thus: 12 volts absent (Low battery) and bad thermostat

 

[Boonieman]

John from Detroit-

I am a new at RV'ing obviously, and after reading many posts from folks like you and others I've tried to do more research on the inner workings on my fiver, so I can understand and do some of my own troubleshooting and repairs. I had looked at all the breaker panels, and on the 120v A/C panel the breakers were labeled in handwriting air cond, furnace, receptacles, etc. So I made a bad assumption that the furnace ran on shore power or the generator. I will check to make sure, but it makes sense for the furnace fan to be 12 volt. I don't mind being wrong myself, but I hate giving out incorrect advice to others. Thank you for your comments, I appreciate that a lot.

Boonieman

 

[JeffPax]

Yea, furnace is always 12v. Has to be available when dry camping. Anyway, agreed that the thermostat was the common thread, new one should arrive today. Will update after install.

 

[JeffPax]

Not good
New thermostat changed nothing

 

[JeffPax]

A/C now working. No idea why. Furnace still not working.

 

[JeffPax]

Furnace working now too. No idea why.
I guess the new thermostat worked after all, don't know why it didn't at first. Only had 3.5V to start with. Now everything is 13+-
Who knows?

 

[John From Detroit]

Bad connection, dirty connection, dead batteries, I had an actual WIRE go bad once.. never seen that before or since but I'm told it happens, right in the "Middle" of the run was a bad spot in the wire...All these can reduce voltage at the load.

 

[JeffPax]

Back to not working again

 

[JeffPax]

Currently, if I slide the selector to "cool", it runs the a/c for one second, clicks, and the a/c shuts off.

 

[JeffPax]

I tried again, 4th time on this set of tries...
It's working again

 

[JeffPax]

Not working again
New symptoms discovered: the voltage at the thermostat will build up to 13+-. If I let it build to full voltage, then slide the selector to "fan", it will run and voltage holds just under 13. Then if I slide to "cool", the voltage instantly plummets to 4 and nothing happens (no a/c). Then slide back to "off" and voltage builds back to 13. If I slide to "heat", voltage plummets to 4 and nothing happens (no heat).
This is surely the same behavior first observed with the original thermostat, just with the added voltage information, which will hopefully help someone diagnose this

 

[John From Detroit]

This is a combination of a bad connection or wire and / or a bad battery.

Measure the voltage at the battery terminals.. I have a feeling you are not well connected.

 

[JeffPax]

The batteries have been a consistent 13.4 volts. I think it's a short as well.

 

[JeffPax]

Checked the converter, it's putting out 13.2
Went up and opened up the a/c, found a wire had slid of the blade connection. Crimped it and it broke. Replaced it with a new blade connector and slid it back on. No change. I can think of nothing else to check within my abilities. Calling the mobile repair guy tomorrow.

 

[JeffPax]

Well, don't ask me to explain it, but mobile RV repair guy replaced the furnace motor and everything works fine again.