Motor needs some drying and tlc

May 27, 2009 6:36 AM

We need to salvage an the blower motor in the our ac unit.

So, our ac wasn't working so well so we decided to clean the coils and such, unfortunately I think we got the motor wet. It will turn on for a while then it flips the breaker. While being 5 seconds or so. What if anything can I do to dry everything out and if I succeed in doing that, will it still work anyhow?

posted by stormygrey to home & garden (12 comments total)

Oh, we have a motor from a newish bandsaw that we swapped out, could we put that in?
posted by stormygrey at 6:38 AM on May 27

The a/c unit outside? doesn't it get wet every time it rains? I'd imagine that the fan motor is in some sort of waterproof enclosure.

As for swapping out one motor for another: the likelihood of the motors having identical, or at least close-enough-for-gummint-work, specs is almost nil. If you absolutely needed to swap out just the motor, get a new one from Grainger or the like.
posted by notsnot at 6:44 AM on May 27

The inside fan and motor part of the deal, not the outside.
posted by stormygrey at 6:45 AM on May 27

Exploring in progress, so new info, I'll leave it alone for a while after this. When trying to run it "fan only" it makes a whining that sounds like the fan or motor is trying to spin, but can't. That high pitched noise that electric motors make when they are physically stopped. Then about ten seconds later it kinda rumbled like it was going to turn, then the breaker flips.
posted by stormygrey at 7:54 AM on May 27

You almost certainly need a new motor. There is zero chance your band saw motor will work. When my HVAC fan died, I pulled it out and took it to a random electric motor supply place. They were able to find a motor that matched my specs for about $50.
posted by Uncle Jimmy at 8:03 AM on May 27

Sometimes motors have "starter windings" that help it get up to speed, and then regular windings that take over to keep it spinning along.
If the starter windings burn out, the motor will behave much like you have described.

THIS IS DANGEROUS, DON'T DO IT:

Sometimes you can "jump start" an electric motor that is in this state. Back home on the farm, we used to do this from time to time.

Give the blade a spin in the direction you think it should go. Try to get it moving pretty good, and then turn the breakers on. If it doesn't work, try spinning it in the other direction.

If you're really brave, you can give the blades a spin with the breakers turned on. This could result in you getting your hand chopped off by the fan blade.

Either way, it's not practical to do this every time you turn on your AC, so you'll likely need to replace the motor.
posted by davey_darling at 8:11 AM on May 27

If the motor is irreplaceable (unlikely), you can have the motor re-wound. I recently did this with a much beloved 1956 Delta Radial Arm saw whose startup torque was ebbing away. Good as new, now. About $250 for the service. Replacing the saw? Maybe $7500 or even more.
posted by bz at 8:14 AM on May 27

I recently replaced my blower motor, I took the old motor to Grainger and they figured out an equivalent motor (had to add a capacitor to mine) i think the cost was around $75. Bonus is that the new motor uses less current than the old one so it's slowly paying for itself.
posted by one at 10:19 AM on May 27

We have a Grainger in the Atlanta area, I guess we'll call it in and try to pick it up tomorrow!
posted by stormygrey at 10:54 AM on May 27

Is it possible that you have some frayed wiring that has gotten wet?
posted by zinfandel at 8:09 PM on May 27

If the motor has gotten wet... you can just dry it out. IF you can remove it (obviously disconnect the power) take the cover off, and put a fan on it for 24 hours or so, making sure it's dry inside. Then close it up and wire it up... might work!

In terms of swapping out the motors.. there are a few things you need to know.

1. Power. The same, or more.
2. RPM must be the same.
3. The insulation rating, related to starts/hour.
4. Shaft size... can you couple it up to the fan?

IANEE (Electrical Engineer)
posted by defcom1 at 10:20 PM on May 27

Well we bought a motor from MSC, it didn't work, we tried using the capacitor from the bandsaw, didn't work, then looked behind the computer board and there it was, a little scorch. With the new motor in, we hard wired around the board and it's running now, albeit continously until we flip the breakers off. We are just trying to find a less expensive way to get the board now. Thanks everyone for your help!

FYI, getting the old motor off was much harder than it should be if anyone else is attempting to do this in the future.
posted by stormygrey at 1:52 PM on May 29