[Wavery]

There is one other safety feature. If the battery goes below a certain voltage (I think it's <11.3V) the circuit board should cut off electricity to the gas valve.

The gas valve has an electro-magnetic solenoid that holds the gas valve open during normal operation. Whenever any of these fail safe devices fail, the control board should cut off current to the gas valve. That will disrupt electrical current to the gas valve solenoid and a spring should slam that gas valve shut.

My guess is, your exhaust pipe may be restricted with debris and/or carbon build-up. Carbon can build up in he exhaust chamber if the propane is not burning properly. This can happen due to debris (spider webs, dust etc) in the fresh air intake, on the outside of the camper.

I would suggest taking out the furnace, giving it a close inspection and cleaning of the outside air intake and exhaust and inside air intake and exhaust. You could even have a dead intruder in the exhaust system. Any debris in the exhaust system will burn at a much lower temp than the high-temp cut-out is set at.

If you contact Suburban, they are very good about helping you trouble-shoot your heater over the phone.

If all else fails, the heater is very easy to remove and take to a shop for repair.

Undo the gas line (lower, right front of the heater), undo the electrical connection, remove the 4 mounting screws on the front and pull it straight out. The intake and exhaust pipes will stay in the camper wall as the heater slides out. This will allow for inspection. It may have one screw holding it to the floor but I have removed 4 of these furnaces and never seen that screw used.

This heater is very simple and easy to work on once it is removed. You can test all of the circuits with a multi-meter before removing the heater. Suburban will tell you what the minimum voltage at each connection (or at least they told me).

I've never heard of the fail-safe systems failing to work on these heaters. The back-ups have back-ups. I think that what you may have smelled was debris in the intake/exhaust burning before your battery went low and shut-off the gas solenoid.