OT: Furnace Blower Problems

On the HEAT side, the electronic pilot lights, and the burner lights, but the blower simply won't start. On A/C, the condenser fan starts, the compressor runs and the evaporator gets cold, but the blower won't start.

The unit has an electronic control box with a green diagnostic LED; LED never blinks a trouble code; just goes bright/dim, which the chart says indicates "normal operation." Obviously, with the blower not working, it is definitely NOT "normal operation." The other night I accessed the blower itself, and the motor spins freely by hand, so the motor's not locked up. I'm planning to pick up a digital volt/ohm/amp meter today to check and see if there's current to the blower from the electronic control box.

Since I'm no furnace mechanic, what else should I check? Filters get changed every 30-45 days, so there's no problem there. Any help or advice would be greatly appreciated, since funds are low [otherwise I'd have called a repair person weeks ago].

Don"t know about any thermal sensor, but the electronic control box has a blower delay microswitch that can be set on 60, 100, 140, and 180-second delay. I"ve messed with that, and the blower won"t come on no matter what the delay setting is.

Blower motor worked perfectly until about 2-3 weeks ago. It ran fine all winter. Breaker isn't tripped, and 20A screw-in fuse at toggle switch on side of the furnace is still good as well. Of course, since it has current to electronic control module, I would assume then that there is current to the furnace...especially since electronic pilot lights when it's supposed to.

Now, I could understand blowing the internal fuse if the amperage was too high; but if the DVOM is set to the proper scale, why would it get fried?

I don't know much about capacitors on these motors; I just know mechanics. Wife THINKS that, because I'm a man, I should know everything there is to know about plumbing, electrical contracting, roofing, concrete, construction, and septic systems...so obviously, since I've never worked in ANY of those fields, and never had training in any of them, I'm a deficient member of the species.

Maybe I'm not to swift on this troubleshooting thing...but I figured that, before I started worrying about capacitors, maybe I oughta check to see if there is any voltage going to the motor to begin with. Is that the wrong way to proceed? I just figured that, if the electronic control module isn't switching power to the blower motor, the problem might well be in the electronic module...and if there IS voltage to the motor, THEN I can investigate why the motor isn't running. Or is my logic faulty in this line of reasoning?

The motor driving the fan could have died, the capacitor that stores energy to help the motor start could have gone bad.

I would suggest if you have current going to the fan that you take it out and drag it to a hvac supply store and have them test the capacitor ( I think you can test a capcitor with an ohm meter ) and motor ( I am sure you can test the windings on the motor with an ohm meter ) and help you out that way.

If you need a new blower motor they can sell you one...