[zaiserchick]

We have a Montgomery Ward 700 furnace with central air. It worked fine all summer. My husband turned the heat on about two weeks ago and all was well. A couple of days ago it started to act up. It would kick on and the blower would come on and kick off in a few seconds. Every three or four minutes this would happen. We shut it down until he had time to look at it. He started it again this morning and it smelled like something was burning. So we bought a new blower motor. He hooked it up and now it doesn't work at all. He has checked the wiring a dozen times. Any ideas on what is wrong or how to fix it??

[letmetellu]

He either has the wiring to the motor connected wrong or it could be that the motor was not the problem in the first place and what ever the burning smell was is probably the problem. Why did he replace the motor in the first place, usually in trouble shooting you try to prove what is not the problem, therefore he should have checked to see if the motor worked before replacing it. Most places that sell motors will not take them back after they have been connected.

[zaiserchick]

He replaced the motor because it was glowing and smoking. Forgot to mention that I guess. Any other ideas? Thanks!

[labman]

If it is an older furnace, they are much easier to trouble shoot. It is possible excessive current to the old motor damaged some of the controls. There should be a limit switch near the heat exchanger that closes when it warms up sending power to a coil of a relay. The relay closes, sending power to the motor.

To do simple checks like this you do need some tools. A test light, a meter, or a voltage detector might be the best place to start with. I came across the niftiest gadget for trouble shooting, a voltage detector. They work through the insulation of wires. There are several brands. I have a GB Instruments GVD-505A, less than $15 at Home Depot. Touch it to a hot wire, and the end glows red. Find the doodad that lights it on one side, and not the other, and you have the culprit. You do not have to open up housings and expose electrical contacts. You are looking at where your hand is, not where the meter is. Most people are capable of doing repairs and will get it going and not get hurt if they use a little sense. The voltage detector makes it even easier.

[zaiserchick]

Whoo hoo... he got it fixed. He had it wired correctly. He tested the old one and the new one. The old one was burnt up. The new one is working great. Also, the switch was worn out. Looks like it fried when the motor went out. Thanks for the help guys!