Belt keeps slipping off furnace blower motor

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  #1  
Old 01-17-15, 04:08 PM
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Question Belt keeps slipping off furnace blower motor

My furnace blower motor belt keeps slipping off and I don't see a way to tighten it.:NO NO NO: Here is the furnace in question and there is a photo of the motor. Do I need to get a new belt? Has it become too loose over the years?

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Last edited by PJmax; 01-17-15 at 09:35 PM. Reason: added picture
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  #2  
Old 01-17-15, 05:27 PM
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You need to lay a straight edge across both pulleys. They must be exactly parallel to each other. Belts do stretch over time. On the back side of the motor mount should be a bolt for adjusting belt tension.
 
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Old 01-17-15, 09:06 PM
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Arrow Just Two Bolts

The only bolts are what you see in the photo. That doesn't look like it will tighten the belt.
 
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Old 01-17-15, 09:37 PM
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There should be four bolts holding the motor to the mounting plate. Are you sure the mounting plate doesn't adjust ?
 
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Old 01-18-15, 08:21 AM
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Could be alot of things. Worn belt and/or drive pulley, too big a belt, belt out of alignment, adjustment device stuck or missing.
Using a straight edge as has already been mentioned will reveal if the alignment is out.
Concerning the picture you provided: look underneath of the motor. There should be a pressed-steel plate with a bolt/nut and rubber pad. That would be the belt tensioner. Or the plate that the motor is attached to will have a sliding channel and bolt going thru it into the blower cage to hold it at the right position. Any time you adjust a belt you should check the amp draw of the motor to make sure it's not overloaded. You're already right there - good a time as any to check the amps.
 
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Old 01-18-15, 09:40 AM
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Arrow Found the adjustment

Well alrighty then ... I found the screw Mr. T was talking about ... but I don't know how to check for amps. Or what reading would mean it is overloaded ... and if so ... loosen the belt? I got it tight where it won't come off with the pulleys moving freely ...
 
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Old 01-18-15, 09:51 AM
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Tighten the adjuster until the belt doesn't have any limp to it. You don't want it to be a guitar string, but, you don't want to to be limp and wobbly.

The old rule of thumb was: when the belt is adjusted correctly, it will flex about 3/4" when pushed with the finger midway between the two pulleys.

To check amp draw you'd need a amp clamp meter. Since you don't have one and don't know what to look for, I'd recommend you have a professional come out and give it a once over. You can probably run it, but why risk damaging a motor?
 
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Old 01-18-15, 11:54 AM
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The plate that your motor is attached to has "legs", one on each side of the plate. I can see them in the picture. They should be slotted and held in place by bolts or screws. Loosening them will allow you to tilt the motor to increase tension. Personally I would not worry about amperage draw on a fractional horsepower motor. Just appearance wise, the motor is probably getting near the point of rebuild or replace. Then again, it could run another ten or more years.
 
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Old 01-20-15, 08:09 PM
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If the belt is over 2 years old I would replace the belt.
 
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Old 01-24-15, 05:01 PM
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Arrow Way Ahead of You

I agree ... I got one in the mail from ebay yesterday.
 
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Old 01-24-15, 05:16 PM
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Have you checked the pulley alignment? Having the pulleys out of alignment will not only cause you to throw belts but wear belts very quickly.
 
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