Furnance Blower Motor Help

[Shep]

My furnance blower motor at my rental property has been acting up. It sounds like gears grinding when it tries to start. I thought the belt was slipping, but after installing a new belt I have the same problem.

My question is this: Is the motor burnt up or due the brushes need to be replaced?

After I put the new belt on the motor did kick on for a few minutes before the grinding/electric sound started up again. The furnance is old, but easy to get to the motor to change if needed.

Any help would be appreciated. I'd like to fix it myself instead of calling a HVAC guy.

Thanks,

[RAFlorida]

Did you check the bearings?

See if the shaft wobbles.
Edit: ment to say that most motors of that sort are brushless.

[Shep]

I checked the shaft, doesn't seem like the bearrings are loose.

[RAFlorida]

Dose the motor have

start capacitor and a run capacitor? These caps may be bad.

[RAFlorida]

Check your PM

You have a message.

[BobSch]

Is it the motor that's grinding or the fan itself? Take the belt off and check for shaft wobble then try spinning the fan by itself.

[eezlock]

furnace blower?

Sounds as if the motor bearings are very dry ( no oil), or the blower wheel bearings & shaft are worn out and very loose! Check these, it will probably
be the problem areas.

[Rich P]

I suppose you've checked for something mechanical, like something hitting the squirrel cage blower or fan?

[master53yoda]

You need to find out if the problem is motor or blower. to do so you remove the belt and run the motor. If the noise does not show up after 15 minutes the problem is probably in the blower bearings. The blower bearings are sleeve type bearings against the shaft. Without oil they will groove the shaft fairly quickly. The blower bearings also have shaft lock washers that position the bearing on the shaft if this washer becomes loose they can be quite noisy.

Belt tension should be 1/4 to 1/2" deflection in the center of the belt between the shafts. Tighter then this will cause noise and fna bearing failure.

Most furnace motors are fractional horsepower shaded pole or split/phase motors. the shaded pole do not have a start winding or switches. The split phase has start windings and a start switch. when starting if you hear a hum , click and change in hum pitch it is a split phase. If it just hums and comes up to speed it is a shaded pole. Shaded pole motors have limited starting torque.

The bearings in the blower and the motor should be oiled every year or season change with 3 drops of oil. that will be 4 locations. use a 3 in 1 oil or a light machine oil. If they have not been oiled in the last couple years double the oil amount.

good luck let us know what you find.

[Shep]

I'll be head back over to my rental on Sunday. I'll check out some of the suggestions posted here. I've never oiled bearings on an electric motor before. Is there an opening on the motor to do this? I'm sure I can figure it out, but would like to have as much info as possible.

Thanks for all the help,

Shep

[master53yoda]

I'll pull my dust filter covers off tonight and take some pictures and post them tomorrow, when I built it I used and old furnace belt drive blower.

this picture shows the oil location

[Shep]

An update

Well, I was trying to get the motor working properly this weekend. It was the motor itself, not the blower unit. I added some oil to the bearings in hopes that it would fix itself. When the unit kicked back on the noise continued, followed by the motor seizing up and, then followed by the worst smelling smoke. So, long story short, I pulled the motor off and am getting a replacement today.

Thanks for all the suggestions.

[master53yoda]

Well, I was trying to get the motor working properly this weekend. It was the motor itself, not the blower unit. I added some oil to the bearings in hopes that it would fix itself. When the unit kicked back on the noise continued, followed by the motor seizing up and, then followed by the worst smelling smoke. So, long story short, I pulled the motor off and am getting a replacement today.

Thanks for all the suggestions.

Well that deals with that, make sure you don't over tighten the belts, and lube it before each season of operation and it will last a good long time.