Furnace running non-stop

Don't know what the problem is but am posting before the tech people solve the problem. Had the trailer (de-winterized) in the yard with the furnace set to come on at 58 because we had a few cold nights. Have a shore power connection but had it disconnected to avoid overcharging the batteries. Went out yesterday to check on battery levels, etc. All was dead. Connected shore power and noticed that the furnace was running non stop. Changed temperature ranges and went to off several times with no result ... still running, although it seemed to be blowing ambient temp. Even turned off the main circuit breaker and it still remained running. Heartland got me with the manufacturer and they had no ideas but sent me in for service. Seems to be some wiring problem at the thermostat and hope the batteries are not damaged after draining to this extreme. Will post the result so y'll can learn as I do.
Regards

The converter in your coach is also a good quality 3-stage battery charger. It will not overcharge your battery. No need to disconeect from shore power.

Dave, Branson is correct. Also, I believe you have a rocker switch in your furnace which will disable it and stop it from running. Pull the panel on the outside of your RV, flip the rocker switch to off while you wait for the tech's reply. Tom

branson4020 said:

The converter in your coach is also a good quality 3-stage battery charger. It will not overcharge your battery. No need to disconeect from shore power.

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Agreed. I left mine on shore power all last summer (and will again this season). No problem.

RollingHome said:

Dave, Branson is correct. Also, I believe you have a rocker switch in your furnace which will disable it and stop it from running. Pull the panel on the outside of your RV, flip the rocker switch to off while you wait for the tech's reply. Tom

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Do you by chance have the furnace and the hot water tank mixed up ?? I don't know of a removable panel on the furnace. There is one on the HWH thou.

"Turning off the main circuit breaker" will have no effect on the furnace, as the fan and ignitor run on 12 volts DC.
The furnace runs for about 3 minutes after the shutoff command to prevent water condesation in the ducts. Did you wait long enough after trying to shut it down?
I would think that if you shut off the gas supply the fan would eventually quit.
Or find the 12 volt FUSE for the furnace, and pull that.