Do I need a new blower wheel or more?


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Old 12-05-16, 12:06 PM
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Do I need a new blower wheel or more?

This Lennox furnace is a pain. It sits horizontally in the attic with rats' droppings around it, and there's so little space to work. Anyway, in the last summer, I heard the banging sound when the AC was running, I shut it off. Now, the cold weather forced me to stop procrastinating. Because the furnace was in a horizontal position, I had no idea where parts of the furnace were when I climbed up into that attic. I quickly plugged and unplugged the power cord to hear where the banging noise came from, I heard it at one end of the furnace, removed the panel ...
I didn't see the set screw. Where did it go? How was it gone?
In the picture, all those three parts can spin independently. Some forum post suggested a new blower wheel.
The system is at least 30 years old.
Do I need a new blower wheel? Should I also get a new motor, too?
In the picture, there is a small hole on the back of the blower wheel. Did this unit have a special set screw and some kind of pin that locked the wheel and the hub together?
I lined all up to show where I thought how they would be when working.
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TIA for any advice.
 
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Old 12-05-16, 12:35 PM
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Thirty years is a good run for a furnace. With a unit of that advanced age it's good to get a routine cleaning where they check the heat exchanger for rust thru and cracks.

In your picture.... the hub (2) is supposed to be attached to the wheel (3).
The set screw locks the hub (2) to the shaft (1).

If the motor is still working... just the blower wheel needs replacement.
 
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Old 12-05-16, 12:41 PM
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With the blower assembly pulled, now is a good time to check the heat exchanger over for cracks or rot before ordering parts. If the heat exchanger is cracked then it's probably time to shop for a new one.
 
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Old 12-05-16, 12:48 PM
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Thanks PJmax.
Per your advice, I ordered the blower wheel just now, $130. It's small enough to fit through the square hole in the closet to climb into the attic.
The architect of my house really did some kind of work. When I need a whole new furnace, the roof must be taken out ...
 
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Old 12-05-16, 02:31 PM
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What does the heat exchanger look like?
It's important that it be inspected carefully in a 30 year old furnace. Cracks mean your at risk for carbon monoxide poisoning
 
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Old 12-05-16, 05:25 PM
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I have to wait for the delivery of the new blower wheel before I open up more panels to remove the motor/wheel assembly. I tried to minimize the number of times visiting the attic to do anything. Through the flashlight's beam, I could see dust flying ... When I came down, I had to take a long shower, washed my hair thoroughly. I also wore prescription glasses, the dust was on the lenses after each trip.
 
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Old 12-16-16, 10:49 AM
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It turned out that I needed new motor, too. Luckily, a friend suggested replacing the motor when the blower wheel got problem; the motor's shaft may bend even though it still spins so I ordered both blower wheel and motor ($120+$320). It took days for the online sellers to find the parts for this weird furnace. The capacitor looked good to be-reused.

I have to say that this was the hardest DIY work ever for me because of the unknowns, the unusual horizontal placement of the furnace, tight space in the attic, the motor "fused" itself to the wheel, small opening in the closet on the ceiling to climb up and down, etc.

In the end, I had to haul the whole assembly downstairs onto the driveway to work on it. No hammer, no puller tool could take them apart. And then a $20 Home Depot snipping tool was used to cut up the blower's blades to get all old stuffs out of the housing. When the blower housing was free and clear, the feeling was much more exhilarating than when I had the old engine mounts taken off my German car. LOL.

After many long days, long hours, long showers to rid the dust, I had the heater up and running again. Thank you for all advice.

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Old 12-16-16, 11:07 AM
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I would never suggest reusing a capacitor. The new motor may require one of different value, plus your old one may be weak. There's no way of knowing the condition of the capacitor without checking with a meter.
Replacing it is cheap insurance.
 
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Old 12-16-16, 11:21 AM
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The sizes, shapes, labels on on both old new motors are identical except one's made in USA, the other in Mexico. It didn't show bulging, ohmmeter verified it as taught on youtube. Funny, I had this Carrier problem concurrently with President-elect Trump saving 1000 jobs at Carrier.
 
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Old 12-16-16, 11:32 AM
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It should be measured via capacitance, not ohms
 
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Old 12-16-16, 11:41 AM
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Hm, google told me this
To test the capacitor with a multimeter, set the meter to read in the high ohms range, somewhere above 10k and 1m ohms. Touch the meter leads to the corresponding leads on the capacitor, red to positive and black to negative. The meter should start at zero and then moving slowly toward infinity.
Capacitors 101 - iFixit
https://www.ifixit.com/Wiki/Troubles...ard_components
 
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Old 12-16-16, 01:00 PM
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I don't see how that method would tell you if your capacitor was weak, beyond its rated value. It would only tell you if the capacitor was open.
I think I have a known weak cap here, I'll try that method now.
 
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Old 12-16-16, 01:08 PM
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No, doesn't work. Tried it with a known weak 5@370 capacitor I found today. Tests to 1.5 mf with my Fluke 116. The ohm test doesn't catch the reduced capacity.
Capacitor should be changed if it's beyond 10% of its original rating.
 
 

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