Presidential II Model 7680C856, blower running constantly

[souta95]

I realize there is already a recent post about blower constantly running, but it is a different model, and I couldn't tell what what to test based on that description.

My mom came home from work today and found that the blower motor was running, despite the thermostat being set to the lowest setting, and the temperature in the house being about 90* at the time. Note, that there is no A/C whit this unit, we have window ones, but they were not running as nobody was home.

We jut moved in to the house a little over a month ago, so we don't know much about it. It was just today that we discovered the "Off" switch on the bottom of the thermostat, flipping that did nothing, and there is no apparent problem with the thermostat (Its a mercury switch one, Jade controls brand). The house is a double wide trailer made (according to the door to the breaker box) in 1980, and as far as I know it is the original furnace.

I used my multimeter to test the thermostat at the molex plug, and it is working normally (continuity when set to on and turned up, open when turned down).

The furnace is hooked up to propane, and I'm not sure if the burner was on or not, my mom said the air didn't feel hot, but that could have been from it being so hot in the house.

The only way I could get the blower to turn off was to flip the switch on the furnace itself. I am not sure what breaker it is, as the one that is labeled for the furnace cuts power to several areas to the house (hallway light, part of the master bedroom, part of the kitchen).

With the power cut, both the "Fan Switch" and the "Lower Limit" have continuity, as tested with my multimeter.

Right now the switch on the unit, and the propane to it are turned off (the propane is off at the furnace, not along the pipe, I couldn't turn that valve)

Any thoughts about the problem and what to do about it? Thanks.

Also, as I was looking around the site, I saw a question about furnace filters for the Presidential II (I don't remember the exact model of that one). When the previous owner was explaining about how to oil the furnace, I asked him about filters for it, and he said that it didn't use them. I imagine that it should have a filter, and if so, what kind does it take, I imagine it's the washable foam one, but I am not 100% certain.

I have a good general knowledge of electronics, but poor specific knowledge of furnaces.

Again, thanks for any help.

[Robert]

Hi,

I would first suspect a faulty Fan & Limit Switch # 7710-3281 .


It can be seen and ordered through PayPal from left side here :

http://www.mobilehomerepair.com/ColemanGas.html




Yes, ALL furnaces need a filter.



You can see and order the filter and filter clips here :

http://www.mobilehomerepair.com/ColemanFilters.html



Just hit continue to shop at first link, then come here to add to cart.



Thanks,
Robert