Furnace won't shut off

[jcmckenna]

I have a 1999 Jayco with Atwood furnace.  The furnace will not shut off automatically.  Replace the thermostat? Any other ideas?

[PattieAM]

Is the just the blower portion of the furnace that won't shut off, or the heat and blower?

Generally, the burner will shut off when temperature is reached, then a minute or two later the blower will shut down.  Then, when temperature drops below the thermostat's setting, the blower will come on first and if battery voltage allows, the sail switch will open and the burner will ignite.

If the fan blows, but there is no ignition of the burner, your battery is below the required 10.5 volts-13.5 volts DC (battery not converter).

You might consider charging your battery and disconnecting it when not camping as your propane leak detector has a 24/7 draw and will kill the battery.

If the battery is not the problem, your next check would be the thermostat.  I found my thermostat had accumulated quite a bit of dirt and had to blow it clean then it worked fine again.

[chasd60]

I have a 1999 Jayco with Atwood furnace.  The furnace will not shut off automatically.  Replace the thermostat? Any other ideas?

Remove the cover from the thermostat and see if the contacts are sticking. I have seen this happen before. Disconnect the battery, separate the contacts and wipe them with alcohol. Allow the alcohol to dissipate and turn the thermostat up and down to make sure it is no longer sticking.

[jcmckenna]

Is the just the blower portion of the furnace that won't shut off, or the heat and blower?

Generally, the burner will shut off when temperature is reached, then a minute or two later the blower will shut down.  Then, when temperature drops below the thermostat's setting, the blower will come on first and if battery voltage allows, the sail switch will open and the burner will ignite.

If the fan blows, but there is no ignition of the burner, your battery is below the required 10.5 volts-13.5 volts DC (battery not converter).

You might consider charging your battery and disconnecting it when not camping as your propane leak detector has a 24/7 draw and will kill the battery.

If the battery is not the problem, your next check would be the thermostat.  I found my thermostat had accumulated quite a bit of dirt and had to blow it clean then it worked fine again.

It's both the blower and the heat.  It happens when the battery is fully charged. The only way to shut it off is to trun off the breaker switch.

[jcmckenna]

Remove the cover from the thermostat and see if the contacts are sticking. I have seen this happen before. Disconnect the battery, separate the contacts and wipe them with alcohol. Allow the alcohol to dissipate and turn the thermostat up and down to make sure it is no longer sticking.

I looked at that and the contacts don't seem to be sticking.

[chasd60]

I looked at that and the contacts don't seem to be sticking.

I would still open them up and wipe them, any conductive particles across them will make it keep running.

Or..................
The system is pretty basic. The only designed contact point is across those contacts. You may have a short circuit somewhere else in the line from the furnace to the thermostat.
 
 Unhook the two wires from the thermostat, making sure to note where they attach, see if the furnace still runs.
 
 If the furnace still runs, you have a problem with the furnace or the wires feeding it. If not, the problem is in your thermostat.

[jcmckenna]

I would still open them up and wipe them, any conductive particles across them will make it keep running.

Or..................
The system is pretty basic. The only designed contact point is across those contacts. You may have a short circuit somewhere else in the line from the furnace to the thermostat.
 
 Unhook the two wires from the thermostat, making sure to note where they attach, see if the furnace still runs.
 
 If the furnace still runs, you have a problem with the furnace or the wires feeding it. If not, the problem is in your thermostat.

Thanks, I will give it a try and let you know how it turns out.

[coach]

It's both the blower and the heat.  It happens when the battery is fully charged. The only way to shut it off is to trun off the breaker switch.

That means turning the thermostat OFF did nothing. I'm thinking bad relay.
Atwood Furnace troubleshooting
My favorite!
Sequence of operations

[jcmckenna]

Thanks, I will give it a try and let you know how it turns out.

Well, it's no the thermostat, I didconnected it and the furnace still ran.
Replace the relay and no luck.

[wavery]

Well, it's no the thermostat, I didconnected it and the furnace still ran.
Replace the relay and no luck.

It is not the battery voltage that you need to measure. It is the voltage at the heater gas solenoid valve that must be a minimum 10.5V.

Your battery may show 12.5 but by the time it gets back to the heater, it could read 11.5 or lower (for any number of reasons), then when the fan kicks in, it may drop below 10.5v. You need to take your voltage reading at the gas valve solenoid with the fan running.

It the voltage is below 10.5 and your battery is charged, you may have a bad ground, battery cable to the converter, bad battery cable to the frame, bad ground at the frame connector, any number of wire connectors could be corroded or lose.

You will need to start at the battery and work back with a digital volt meter (or multi-meter). Anywhere that you find a significant drop in voltage, you have a problem. You may find multiple problems too.

The other thing that you should check is the gas solenoid valve itself. If it is getting 11v (with the fan running) and is not opening, you may have a bad solenoid valve. The solenoid valve needs 10.5v minimum to open and let gas into the furnace.

The other thing could be the ignitor. Turn your heater off at the heater and at the thermo. Turn the temp down all the way. Let it set for 10 minutes. Turn the switch on at the heater, wait for 5 minutes. Turn the switch on at the thermo. The fan should turn on. After about 1 minute, you should hear the ignotor click. It should click once every 30 seconds. It will do that about 3-4 times then the fan should shut off automatically. If you don't hear that clicking, you may have a bad ignitor. .......(be sure you have gas in the tank and the tank is turned on).

[wavery]

Well, it's no the thermostat, I didconnected it and the furnace still ran.
Replace the relay and no luck.

Are you saying that the furnace is producing heat and the fan stays on?

What happens when you turn off the electric? Does gas continue to flow into the furnace...with the fan off? :yikes:

Are you aware that there is a switch inside the furnace cover? What happens if you turn that off?

[chasd60]

Well, it's no the thermostat, I didconnected it and the furnace still ran.
 Replace the relay and no luck.

Try disconnecting the wires from the thermostat AT the furnace.
Not sure if you did that or just disconnected them from the thermostat (t-stat)?

A short circuit in the wires anywhere between the t-stat and the furnace can cause it to stay on just like the t-stat was calling for heat.