Trouble with Coleman 2880C766 gas forced air furnace

[rsiders]

Hi,

I've got a Coleman 2880C766 that's acting wonky. Here's how:

I have periods when the furnace works like a champ... it cycles on and off perfectly and keeps the house comfortable. Sometimes these periods last a month. Sometimes a week or so. Sometimes it's just a few hours. Sometimes it only does what I describe next.

But other times, like right now, the furnace has what seems like a short cycle, the blower shuts off abruptly but the vent motor still runs. The cycle is not long enough to satisfy the thermostat. Also, after the blower stops, the vent motor will run for hours if I don't shut the thermostat off (and sometimes it does run for hours because, when it happens, it's almost always at night while I'm asleep or during the day when I'm at work). When this happens, the furnace doesn't kick on until I shut it off and then turn it back on (or if I go into the furnace room and open the blower door switch). From there, it's a crapshoot whether I'll get proper operation... sometimes yes... sometimes no.

Lastly, if I turn the t-stat to Fan for continuous I get nothing except for silence. The fan never comes on.

Other key particulars:
1. I'm aware that I'm going to have trouble finding parts.
2. My project for today is cleaning the blower motor, the blower wheel and housing.
3. I can e-mail the wiring diagram.

My thoughts... mind you, I know next to nothing about furnaces. But I'm a reasonably smart guy and somewhat handy...

1. Dirty/dying blower motor.
2. Bad module.

Thanks in advance!

[HayZee518]

this is hayzee, send me the diagram. my email is in my profile

[rsiders]

Thanks for taking a look. I sent the diagram just a few minutes ago.