Furnace Problems????

[DOUG & DONNA TROTT]

My brother is having trouble with his furnace and I was wondering if anyone has had the same or similar problem.

It has a Coleman Mach thermostat on it.

The Furnace is an Excalibur 8500 Series III

When the heat is turned up to say 85 or 90 the unit will ignite the burner and it will heat up there box and then the blower will come on, as is normal, but if he turns move the thermostat back to say 75, the burner will go out the unit will cool down and turn off, as is normal, but the unit will never come back on even if the trailer gets cold unless the thermostat is switched to the off position and them back on and then, it may not work the first time, but will eventually get it to come back on.

I am thinking the thermostat has suffered a malfunction and should be replaced, but he is not mechanically or electrically inclined to check the furnace or thermostat.

We are about 400 miles apart, so I am not going to be able to help him much, other than seeing if anyone has had the same or similar problem and maybe see what kind of solution fixed the problem.

HELP!!

["007"]

In this sticky above it has info on Atwood heater and problems with 8500-8900 heaters may help.

[Lin Duh Lee]

Doug, If the burner is igniting before the blower comes on that is not normal. You need to have a qualified tech check your furnace. The blower should always come on before the burner. Don't compromise safety to save a buck or two.

[DOUG & DONNA TROTT]

It operates correctly the "first time". After it has satisfied the thermostat and it turns off by it self, it will not turn anything back on. The blower will not start nor will the gas valve open. Turning it off and on a few times and it will then again start and run correctly until it cuts off after satisfying the thermostat.

They are living in the unit right now as they are building a new house out on the "Ponderosa" and the forecast is for snow tonight.

He got it to running again and left the thermostat on 90 to see what would happen. It cycled correctly a few times and shut down well before reaching the 90 degree mark. It then would not come back on when the temp in the coach dropped.

[oldbeek]

Set at 90 it should not cycle on and off. Limit sw is cycleing open and closed. Cause, not enough air flow. It will do this 6 times and then the board shuts down for 60 minutes before starting the cycle again.