Atwood Furnace problem - blower will not shut down
Hi, I am having a problem with my Atwood furnace in my 2016 Jayco HT Eagle 27.5RLTS. Just went on a camping trip above Syracuse, NY and used the furnace for 4 days with no problem at all. As we were preparing to pack up and come home, the furnace blower kicked on, but no heat came on. The furnace blower continued to run, even when I set the thermostat to off and the temperature to the lowest setting. The furnace blower ran nonstop for a couple of hours while we packed up. Finally, I got it to shut down by pulling the 20 Amp fuse for the furnace.
When I got home, I set up the trailer, connected power and turned on propane, checked the stove and the fireplace and those all worked fine. Had the thermostat still in off position and lowest temperature setting. Put the 20 amp furnace fuse back in and the furnace blower immediately started running again, but no heat. Looked through the manuals on the furnace and saw that there is a power switch on the unit. I opened the grill in front of the furnace, found the switch and turned it off. Furnace blower stopped. However, with this switch turned off, the AC and the fan no longer function. Thermostat settings have no effect. Turned the furnace power switch back on and furnace blower starts running again, still no heat. AC and fan now function properly using thermostat. Finally, I turned the furnace power switch off, turned off the 30 amp main A/C breaker and disconnected the battery. Then I reconnected the battery, turned on the 30 amp A/C breaker, and turned on the furnace power switch. At this point, the furnace blower did not start running again. I checked the AC and fan operation with the thermostat and they work fine. With the thermostat set to the lowest temp, I turned the thermostat switch to Heat. Still no activity from the furnace, as expected. Checked the stove and propane is working fine. Slid the thermostat temp up until I heard a click and the furnace blower came on. Waited 5 minutes, but no ignition on the furnace burner and the blower continues to run. Had to repeat above procedure to get the furnace blower to stop running.
I have seen a post that mentions a high limit switch as being the culprit. Where is this switch and how do you get to it? Looking at my furnace unit, it is a sealed box with only the power switch on top being accessible without removing the whole unit.
Is there a simple fix to this problem or am I stuck taking my 5th wheel back to the dealer (over an hour away)?