Noisy motor

[hbiss]

I have a Modine gas fired unit heater with a draft inducer blower. It makes a loud grinding or growling sound when running. I traced it as coming from the little 1/9 hp/3000 rpm draft inducer motor. I originally suspected bad bearings (sealed ball bearings) or a clogged up unbalanced blower wheel but on close examination I see that the motor is only noisy when power is applied. When it is shut off, noise stops immediately and it will coast smoothly for almost 30 seconds making absolutely no sound. You can see the shaft out front and cooling fan inside the motor through slots and see that the armature does not move backwards or forwards when powered or power is removed. There does not seem to be any lateral play.

This is a capacitor run motor and for giggles I'm going to replace the 4 uF cap and see what happens. Any other ideas?

-Hal

 

[mtnelect]

I have a Modine gas fired unit heater with a draft inducer blower. It makes a loud grinding or growling sound when running. I traced it as coming from the little 1/9 hp/3000 rpm draft inducer motor. I originally suspected bad bearings (sealed ball bearings) or a clogged up unbalanced blower wheel but on close examination I see that the motor is only noisy when power is applied. When it is shut off, noise stops immediately and it will coast smoothly for almost 30 seconds making absolutely no sound. You can see the shaft out front and cooling fan inside the motor through slots and see that the armature does not move backwards or forwards when powered or power is removed. There does not seem to be any lateral play.

This is a capacitor run motor and for giggles I'm going to replace the 4 uF cap and see what happens. Any other ideas?

-Hal

Save yourself a lot trouble ... Replace the whole assembly, three screws at most that secures it.

 

[ActionDave]

You might get lucky with new bearings. A capacitor ain't gonna fix it. Bearings coast freely when they are worn out and there's not enough grease in them to slow them down. If the end bells are worn out the motor is done for. It's noisy when power is applied because the rotor is being sucked against the stater. There's only a couple thousandths clearance so you won't see it move but on the workbench you can feel the play if you gently press on the motor shaft.

 

[ptonsparky]

For giggles, have you checked the winding resistance and megged it?

Compare to the new motor.

 

[hbiss]

Save yourself a lot trouble ... Replace the whole assembly, three screws at most that secures it.

You can't find parts for that thing. Similar motors for other models are over $250. Whole blower assembly over $700 !!

You might get lucky with new bearings...

Nahh, you can't get that motor apart. Cheap Fasco.

-Hal

 

[ptonsparky]

Have you tested the capacitor?

 

[TwoBlocked]

Cracked rotor? I think you can put low voltage a/c (doorbell xfrm?) on one coil and see how the sound changes as you rotate.

 

[ptonsparky]

Everything can be disassembled. May never work again...but

 

[ActionDave]

Nahh, you can't get that motor apart. Cheap Fasco.

-Hal

Bet you can. If it has those metal clips that hook down into the vent holes of the end bell you can get them out by poking a small screwdriver under the hook and pop them out. You have to be careful that they don't fly across the room and disappear.

 

[DooWop]

If the cap is OK then it sounds like the bearing is worn enough to cause the rotor to run too close to the stator.
Used to be fractional motors like this weren't worth repairing. Knowing Modine, it sounds
like it might be worth it if you can find a shop that will take it.
I once worked in a town that had a lot of really old heating equipment. Many motors were obsolete and had been for years.
There was a shop there that would repair most things I brought in.