AC running while off ????

[SueRan]

Not the fan but the roof unit in my older 2005 Forest River Salem fifth wheel is coming on and off with the thermostat in the off position. This can't be good. Any ideas?

[14apex]

Originally Posted by SueRan

Not the fan but the roof unit in my older 2005 Forest River Salem fifth wheel is coming on and off with the thermostat in the off position. This can't be good. Any ideas?

With my basic (very) understanding of the "system" my initial guess is that a relay is "stuck". That would possibly be found integral to a control unit...maybe in the ceiling (inside) unit and it may be difficult to diagnose...must use VOM, etc.. It could be the thermostat itself, of course. ...may be worth a service call from an RV HVAC technician if you're not handy with it. If time and $$ are not major issues, you could identify and order both the control unit and t'stat, "hoping" that the issue departs with the old stuff.

[jbflag21ds]

if you remove the yellow wire from the t-stat, will it continue to run? If no, then the t-stat is bad. If yes, then the board on the a/c unit has issues.

[Bama Rambler]

Tell us which A/C and thermostat you have?

Your problem is likely the thermostat, but once we know what we're dealing with we'll know more.

[SueRan]

Thanks the thermostat is a Dometic cool/furnace, the original that came with the RV. It does have some give on the wall. I don't feel comfortable messing with the wires. I turned it off at the breaker last night as the noise it makes coming on and off every few minutes is annoying.

[Bama Rambler]

That's an older analog thermostat, they don't normally go bad in the manner you describe, but they can.

The wire under the GND terminal looks loose. This runs off 12 volts so it doesn't pose a safety issue. However, it would be a good idea to disconnect the battery.

Do you feel comfortable gently tugging on the wires one at a time, especially the wire under the GND terminal to see if they're loose?

[SueRan]

They all feel snug to me. I just ordered a new one, I'll pay someone to change them out. If I still have issues I guess I'll have to call a RV Repairman. Ugh..

[Bama Rambler]

Please keep us posted on how it works out. Hopefully it fixes the issue for good.

[bikendan]

Originally Posted by SueRan

They all feel snug to me. I just ordered a new one, I'll pay someone to change them out. If I still have issues I guess I'll have to call a RV Repairman. Ugh..

It's actually a very simple replacement.

[mnoland30]

Thermostats generally run on 12 volts, and are completely safe to work on. If you're not plugged into AC power from your house or a pedestal, then everything in your trailer is 12 volt and safe to work on. It is a good idea to take a picture before taking things apart. The blue plastic that the wires go into have screws that tighten to hold the wires. If any wires are loose, use a small screw driver to tighten by turning clockwise. If the wire is out, then loosen first, stick the wire back in, and then tighten. The more you know about your trailer, the more comfortable you'll be working on it. This forum will help. I've never taken mine to a dealer, but I've heard horror stories of it taking all summer to fix things. If you get a Volt Ohm meter, you can check the voltage on anything to make sure it is safe to work on.

[SueRan]

Replaced the thermostat, same issue. Ordered the control board, if that doesn't work I'll have to replace the unit which is 800 to 900 $$. With install I'm just not sure if I should put that much money in this older RV. Any thoughts?