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Old 08-17-2011, 11:39 AM   #1
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lennox blower motor help


I have an older lennox downdraft furnace. The blower motor recently quit working while using the a/c. The outside unit is working as it should. I switch the t-stat fan switch to on and the blower still did not start up. I also tried to turn the furnace on, the burners fired up, but the blower still did not kick on.

I have been pretty good about changing my filters every 30 days, however, upon further inspection it was quite dirty inside. Even if I get it going I think I should still pull the blower and clean it.

When I turn the fan to the on position, I am getting a buzzing sound. The buzzing sound is coming from a wiring box located to the left of the cam-stat and gas valve. Will there be a capacitor inside that box? Any tips on how I can determine if this is a bad capacitor or motor?

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Old 08-17-2011, 12:20 PM   #2
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You need a multimeter with MFD in order to test the capacitor. By your description sounds like capacitor problem.

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Old 08-17-2011, 12:58 PM   #3
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I do have a multimeter. I will check to see if it has that function. I think I see the capacitor is on the front of the blower motor housing. It is oval and has three connections. Looks like two black, one green. Would that be it?
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Old 08-17-2011, 01:28 PM   #4
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lennox blower motor help


yes it's the capacitor. This capacitor should have only 2 terminals.....can you post a picture?
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Old 08-17-2011, 01:50 PM   #5
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lennox blower motor help


try spinning the motor. should be able to turn it easily with 1 finger. if not it is seizing up. those capacitors rarely fail. post the model # of the furnace.
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Old 08-17-2011, 02:26 PM   #6
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Here is a pic of the capacitor. I do not see it leaking or bulging, however it is dented in near the bottom. Don't know if that means anything.

Wheel moves freely. I tried carfuley spinning it to jumpstart it but no help.

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Old 08-17-2011, 02:37 PM   #7
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lennox blower motor help


Don't not touch the terminais with your hand. If you need to replace, first discharge it. Disconnect the wires, mark the wires positions. With multimeter on MFD, you can check the capacitor.
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Old 08-17-2011, 02:51 PM   #8
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I have a el-cheapo multimeter from harbor freight and I dont think it has MFD.

When the blower motor quit I was home and did not notice any burning electrical smell. After checking the tstat and breakers i opened up the furnace and the blower motor was warm, but I would not say it was hot. I could hold my hand on the motor. Just trying to give more info.

I may just replace the capacitor to rule that out since it should be fairly cheap. I have heard of discharging them with a well insulated screwdriver. Bad idea? What would you do?

Thanks for the advice so far.
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Old 08-17-2011, 03:06 PM   #9
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lennox blower motor help


Quote:
Originally Posted by fishon1213 View Post
I have a el-cheapo multimeter from harbor freight and I dont think it has MFD.

When the blower motor quit I was home and did not notice any burning electrical smell. After checking the tstat and breakers i opened up the furnace and the blower motor was warm, but I would not say it was hot. I could hold my hand on the motor. Just trying to give more info.

I may just replace the capacitor to rule that out since it should be fairly cheap. I have heard of discharging them with a well insulated screwdriver. Bad idea? What would you do?

Thanks for the advice so far.
Turn off, discharge for your safety.
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Old 08-17-2011, 03:27 PM   #10
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So my pic is the capacitor correct?

The capacitors I have seen for sale online do not look like they have a ground connection. Whats up with that?

So the screw driver method is Ok?
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Old 08-17-2011, 03:35 PM   #11
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lennox blower motor help


So my pic is the capacitor correct? Yes

The capacitors I have seen for sale online do not look like they have a ground connection. Whats up with that?

Capacitors can be oval, cylindrical etc.. I dont know about ground connection.
You need to look for:
5MFD 370V
5MFD 440V
7MFD 370V
7MFD 440V

So the screw driver method is Ok? Yes
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Old 08-19-2011, 02:18 PM   #12
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I changed the capacitor and that did not help. I figured it was the blower motor but I did not feel comfortable changing it myself. I went to All Hours Heating and Cooling down the street and they came by this morning and swapped the blower motor out. They also cleaned up the wheel, and changed my heat to a higher blower setting, which it needed. Total cost was $280. Oh well, all is good now.

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