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Old 12-16-2007, 03:24 PM   #1
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Gas furnace blower won't come on


We have a very old (30+ years) Sears gas furnace that has been well maintained. The blower suddenly stopped functioning. The pilot light stays lit, the burner comes on and stay on for approx. a minute then just shuts off. The blower never comes on. I know it's ancient and probably inefficient, but replacing it is not an option right now. Help? Please?

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Old 12-16-2007, 03:40 PM   #2
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Gas furnace blower won't come on


Assuming you have central ac I would have you turn the fan selector switch on your thermostat from auto to fan on. If the fan comes on the problem may be your combination fan and limit control. If so leave the fan on and the heat will cycle on and off, for temporary use. If fan stays off it will most likely be the fan motor. Turn 120 volt power to furnace off, remove bottom door, and carefully touch end of motor to sense extreme heat. One other possibility may be the motor run capacitor.

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Old 12-16-2007, 03:46 PM   #3
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Gas furnace blower won't come on


Carriertech - I appreciate your quick reponse. I do not have central AC so am unable to check the fan in the manner you suggested. Any other ideas? I've wondered about the settings on the limit control. They've not been changed to have caused a problem but could they need adjusted?

Last edited by lindan; 12-16-2007 at 03:49 PM.
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Old 12-16-2007, 03:57 PM   #4
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Gas furnace blower won't come on


I would still check to see if motor is hot and see if blower wheel spins freely. Power off during this time. Then we can try to locate the fan control in the top area of the unit. May have silver cover that pulls off then you will see a round dial. Power on at this time. Advancing the dial would simulate normal operation and turn fan on, but if switch or motor are bad you still may have to pay that damn tech. Good luck nobody wants to spend the xmas $ on a furnace.
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Old 12-16-2007, 04:24 PM   #5
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Gas furnace blower won't come on


Motor is not hot and the blower wheel moves freely.

The limit control is set on 180. There are 2 fan dials. One says "fan off" and goes from 80-120. The other says "diff" and has 20, 40, 60, 80. I turned the "fan off" dial and get a clicking sound but that's it.

And you're 100% correct. With 4 kids, 3 of whom are in college, I have to do as much DYI as I can...especially at Christmas. There's going to be very little as it is...don't want to reduce it even more by having to pay for furnace repairs.

Last edited by lindan; 12-16-2007 at 04:54 PM.
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Old 12-16-2007, 04:56 PM   #6
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Gas furnace blower won't come on


Sorry LInden that sounds like a cam stat type switch. Does the thing but looks different. I'm afraid without being able to discuss voltages I'm not sure I can help. If we could use a meter to check for 120 volts at the motor leads and work are way back through the switch, to the source we could find the culprit. wish I could be of more help.
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Old 12-16-2007, 07:45 PM   #7
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Gas furnace blower won't come on


Here's a link to a photo of the limit & fan switch. http://s40.photobucket.com/albums/e2...ndapics137.jpg

Does that help at all?
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Old 12-16-2007, 11:05 PM   #8
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Gas furnace blower won't come on


Hopefully Carriertech is stil helping you out trouble shooting this.

If you are still busting on it I'll see if any of this helps.

It sounds like your furnace and its safety features are working as they are designed. Thermostat signals burner on, burner lights, blower gets signal to turn on or just a completed circuit turns blower on, furnace chamber heats up but blower never moved any heated air so safety trips burner off.

Seems like the story. Everything happens for a reason. If you have a multi-tester for electricity and know how to safely use it, that would be good way to figure this out. I'm just a farm kid living in the big city so what I know for sure and $5 might get you a good cup of coffee somewhere. What I'm saying is you can probably figure it out and you can probably eventually fix it yourself but if you haven't the time or the safety awareness to do this, give the pros a call and eventually get yourself a good nights sleep.

If it were were mine I would look at the wiring diagram and see wher the blower comes into the electrical loop. I'd find its wiring and I would safely run the proper electrical juice to its leads and see if the blower would run. I mean if its a safety switch or relay that's out I'd like to eliminate those as I move along. Your furnace is just a bunch of inter-connected parts with pieces that can be isolated and trouble-shooted out. Without knowing your furnace, I'd check blower, blower relay, fan and limit control , and I wouldnt think any aquastat because the blower never kicks on. Good luck. Cliff
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Old 12-17-2007, 09:11 AM   #9
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Gas furnace blower won't come on


UBoiler - Thanks for the tips. My brother is an electrician but is out of town or I'd get him over here! I think I may be able to borrow his volt meter. I'm not wanting to wait until my hubby returns. It got to 23 degrees last night, but I stayed warm with an oil filled electric heater in my room.

Anyway, thanks again. I'll look into the wiring.
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Old 12-17-2007, 10:57 AM   #10
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Gas furnace blower won't come on


There are three wires coming into the limit switch.

What does the yellow, black and brown one have written on the limit switch?

COM?
LINE?
LOAD?


You shold be able to connect two of these to see if the motor will rotate.
If the motor rotates then the motor is good.

If the motor does not rotate then the limit switch may be bad.

Can you post a photo of the wires as they connect to the motor?

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