DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > Older Furnace Blower Motor doesn't turn on




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Old 02-05-2010, 09:28 PM  
1victorianfarmhouse
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Default Older Furnace Blower Motor doesn't turn on

Nice to find some forums to read that aren't 10 years old and dead...

I recently bought an older victorian house, and the main gas furnace (Armstrong) is from 1996 but worked fine....for about 2 weeks.

The blower motor does not start up. It seems to want to start and moves very very slowly, but even with help turning it, it won't stay running. The fan turns easier before and after the fan tries to kick in.

I had a HVAC repairman take a look at it today while I was gone, and he told me the fan had frozen stuck, but he was able to loosen it, and get it running though the bearings were bad and I would be best to replace the furnace.

It's already not working again. I find the fan turns awfully smoothly for having bearings that were stuck just this morning. No noise or roughness. I am wondering if there's a limit switch type of apparatus that I should look for, or the motor itself is probably going bad. The fan itself looks very clean.

Comments welcome and greatly appreciated. I'll be able to post more details once I know what info people need to know.

Thanks,

vince



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Old 02-06-2010, 08:09 AM  
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Sounds like the capacitor is shot. There only a couple of bucks ($10) so I'd change that out for starters.



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Old 02-06-2010, 06:31 PM  
1victorianfarmhouse
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Thanks for the quick and helpful reply!

I found the capacitor, it's an Aeromet II. The only shop near me was closed, so I'll wait until Monday.

In the meantime, I've found out that when the furnace sits for an hour or two while not trying to start, when it does try to start, it will start and run like normal for about 20 minutes then shut down. Then it will try to start again, and be unable to get the fan blower turning, like I mentioneed in the original post.

Thanks again,

vince

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Old 02-07-2010, 09:03 AM  
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Ok, hold on a minute; which blower motor are we talking about?
This no longer sounds like a bad capacitor.

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Old 02-07-2010, 09:09 AM  
1victorianfarmhouse
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Uh oh,

This is the big fan blower motor, not the smaller one.

After having the furnace shut off all night, I flipped the switch and it started and ran like normal again for 15 mminutes before shutting off and being unable to restart the big fan blower motor, just like before. shutting it off for an hour, it still wouldn't restart the big blower motor. I suppose that when I come back in a few hours, I'll be able to get it too start after sitting.

Thanks help any?

Thanks again!

vince

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Old 02-07-2010, 01:33 PM  
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Ok that's what I assumed from the start however, being that it does start and run as normal for a brief time, indicates that the capacitor will most likely not be the issue.
What the problems could be are:
-Unit is shutting off on high temp limits (allowing the unit to cool down will enable restart).
-Blower motor is tripping out on thermal overload this could be attributed to bad bearings causing an excessive load on the motor (as the technician has identified).
A replacement motor could be as much as $250, depending.
Regardless; if the burners continue to run without the blower fan running, it will eventually shut down due to high temp limit switch being tripped. This is apparently an auto-reset switch. Turning the unit off at the service switch may reset the overload. I would try to nurse a little oil into the blower bearings (assuming their not permanently sealed bearings) and see if it can't be revived. The capacitor is used for starting the blower but, once up and running the capacitor drops out of the picture and can not be blamed for the blower motor shutting down.

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Old 02-07-2010, 05:26 PM  
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Hi, and thanks again for the reply.

A friend of mine came over to visit and see the house. He's a mechanical engineer who prefers to fix foreign cars and is very good at it. He's also replaced most of the parts of the furnaces and a/c units at his shop and house.

He listened to the motor trying to start and he says it's the capacitor.

I was thinking that maybe the motor was heating up and the bearings were causing drag when warm, but there is no apparent drag when turning the fan, either cold or warm, only when it's trying to start. I've had plenty of old electric motors with dry or seized bearings, and this just didn't feel like that. I do agree about trying to get oil into the bearings, though my friend told me how AC motors last far longer than DC motors as they have no brushes and only need to worry about dirt, and the fan and area was very clean.

I do wonder if there's a thermal switch that might also be malfunctioning. The time needed for cooldown seems to take a very long time, an hour or more at 50 degrees, yet I'm able to put my hand on the back of the blower motor when it stops without getting burned.

I also found the user's info manual for the furnace, so that is interesting to have and read through.

Tomorrow I should be able to get a capacitor, we'll see if that makes a difference!

Thanks,

vince

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Old 02-07-2010, 09:01 PM  
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I suppose a bad start capacitor could theoretically shut down a motor on thermal overload.
The cool down I was referring to was for the heat exchanger not the thermal overload however, both require a time-out to cool down.
Good Luck and let us know how it works out

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Old 02-08-2010, 11:51 PM  
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Well, I replaced the capacitor, but the blower motor still shuts off after running for about 15 minutes. So, new motor time, I think. Good thing is that I found a great shop to get parts from!

More to come,

Thanks,

vince

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Old 02-09-2010, 09:53 AM  
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Quote:
Originally Posted by 1victorianfarmhouse View Post
Well, I replaced the capacitor, but the blower motor still shuts off after running for about 15 minutes. So, new motor time, I think. Good thing is that I found a great shop to get parts from!

More to come,

Thanks,

vince
Can you just jumper the motor (supply it with 110v) and see if it kicks out after a time? maybe the problem is with a controller, not the motor itself


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