I think I need a new start capacitor.

[gayler]

My furnace blower is slow to come up to speed and is noisy as it spins up. Once it is up to speed it is not noisy. Does this sound like the problem? Do I need to discharge it before I disconnect it? Also does my current one look to be the right size for my furnace? I didn’t see a label on the blower motor for specs.

 

[rkevins]

that is a run cap, it could be the problem but you could also have a motor getting ready to go out or lock up. they should be pretty cheep at a supply house.

 

[gayler]

that is a run cap, it could be the problem but you could also have a motor getting ready to go out or lock up. they should be pretty cheep at a supply house.

Does it also have a start cap? I didn’t see another one. The motor spins free and is not noisy when up to speed.

 

[gayler]

Here is a couple more pictures.

 

[The Cobbler]

does the motor spin easily & freely by hand? I'm wondering if it's dry on lube.

 

[gayler]

does the motor spin easily & freely by hand? I'm wondering if it's dry on lube.

Spins free by hand and no noise spinning by hand. The only time it’s noisy is as it spins up to speed, which takes about five seconds . Once up to speed it’s not noisy either.

 

[lonestardiver]

You can test the capacitor, some multimeters have a capacitor test function. Granted those caps are not expensive.

 

[Innovate1]

What type of noise? Does the unit vibrate much as it comes up to speed? Could be a resonance in the duct work. You could take the motor out and try spinning it by hand - the inertia of the blower wheel will make it hard to feel small amounts of roughness in the ball bearings. Are the bearings ball or sleeve?

Most blower motors have only one capacitor. No way to tell if it's the right value without more info - the value varies with motor design. No need to discharge it - the motor will do that.

Did it become noisier over time? Or is this a unit that is new to you so you have no history?

The caps do go bad. Find a way to measure it or get a replacement to try.

 

[AP514]

Your pic's are out of Focus hard to read anything on them.
Also take a closer shot of the wire diagram. Aroung the Cap Area

 

[gayler]

Your pic's are out of Focus hard to read anything on them.
Also take a closer shot of the wire diagram. Aroung the Cap Area

I will try to get better pictures tonight when I get home.

 

[alfredeneuman]

Does it also have a start cap?

Some capacitors (permanent split capacitors) have both start and run windings together in the same case.

 

[Terry D]

That is the only capacitor. It stores voltage to give a little extra jolt to get it up and running. A 5 mf is a common one for blower motors. Has it ever been changed before? You probably would have to pull the blower housing out to be able to see the label on the motor. Most times they bleed off voltage, but it never hurts to short it with a screwdriver first. If you dont have a way to test it, the supply house or motor shop might do it for you. But as already said, the are pretty cheap to buy.

If that doesnt fix the problem, then you might be looking at replacing the motor

 

[gayler]

That is the only capacitor. It stores voltage to give a little extra jolt to get it up and running. A 5 mf is a common one for blower motors. Has it ever been changed before? You probably would have to pull the blower housing out to be able to see the label on the motor. Most times they bleed off voltage, but it never hurts to short it with a screwdriver first. If you dont have a way to test it, the supply house or motor shop might do it for you. But as already said, the are pretty cheap to buy.

If that doesnt fix the problem, then you might be looking at replacing the motor

Thanks Terry. I'll see if I can get one tonight.

 

[Bert_]

That is the only capacitor. It stores voltage to give a little extra jolt to get it up and running. A 5 mf is a common one for blower motors. Has it ever been changed before? You probably would have to pull the blower housing out to be able to see the label on the motor. Most times they bleed off voltage, but it never hurts to short it with a screwdriver first. If you dont have a way to test it, the supply house or motor shop might do it for you. But as already said, the are pretty cheap to buy.

If that doesnt fix the problem, then you might be looking at replacing the motor

It doesn't store voltage to give it a jolt.

The capacitor creates a phase shift. It's sort of like creating a third phase.

 

[dogdog]

Spins free by hand and no noise spinning by hand. The only time it’s noisy is as it spins up to speed, which takes about five seconds . Once up to speed it’s not noisy either.

I have this problem with an old drill press motor, I did ask about it here and it end up being dried lube on the centrifugal switch mechanism... I took it apart and lube up everything and it's been fine since. 1/2HP for my motor.

Your situation might be a bit different , I don't know what kinda of motor you have (pic is blurry) or if your motor even have a centrifugal switch inside at all (it's inside the motor, usually), especially if it is a fan motor it's iffy. Usually if your motor starts fine, it's not the startcapacitor.

so YMMV.

 

[Bert_]

I have this problem with an old drill press motor, I did ask about it here and it end up being dried lube on the centrifugal switch mechanism... I took it apart and lube up everything and it's been fine since. 1/2HP for my motor.

Your situation might be a bit different , I don't know what kinda of motor you have (pic is blurry) or if your motor even have a centrifugal switch inside at all (it's inside the motor, usually), especially if it is a fan motor it's iffy. Usually if your motor starts fine, it's not the startcapacitor.

so YMMV.

It's a PSC motor. It doesn't have a start switch.

 

[dogdog]

It's a PSC motor. It doesn't have a start switch.

thx learned about something new.

But either case, humming I would suspect capacitor, squealing, I would suspect mechanical issue though. maybe chuck it up to a drill or rotate it a bit faster and see if you can hear it.

 

[gayler]

Got a new capacitor. I’ll get it in after lunch. It’s a USA made Titan brand 5 MFD 370 volt.

 

[Wrench97]

And your old one is a 440VAC rule of thumb you can always go up in voltage rating but should not drop down for a replacement cap.

 

[dogdog]

....

 

[gayler]

And your old one is a 440VAC rule of thumb you can always go up in voltage rating but should not drop down for a replacement cap.

Yes that is true, but we’re talking about a 120volt motor so I would say I’m good either way. I pulled my old one which was rated at 5 MFD plus or minus 5% and it tested at 3.75. The new one also rated at 5MFD tested at 4.95. After changing it the blower is much quieter and starts some what quicker so I’m calling it a win.

 

[The Cobbler]

.... I’m calling it a win.

Great!