Blower Won't Activate with Thermostat

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Old 12-07-10, 09:42 AM
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Blower Won't Activate with Thermostat

I have a Lennox G20 gas furnace. For the last couple of days, the blower has not activated on the thermostat's command as the house temperature drops. The thermostat activates the furnace flame, and we can observe that the furnace heats automatically, but the furnace doesn't blow air through the house automatically. The blower does function when we set the "fan" switch on the thermostat to On instead of Auto. Any idea what's going on and what we should do? Thanks.
 
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Old 12-07-10, 10:28 AM
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Well..the Pro's may know more...but here's a thought. The ON position is normally HIGH speed, same as the A/C is normally set to. Heat normally uses a lower speed such as MED or MED HIGH...depending on how many are available with your motor.

Could be the windings for MED are burnt out.

Could also be some sort of relay or control board.

If you have a meter, you should be able to go up and check for power on the MED speed wires.

As I said...just some thoughts.
 

Last edited by Gunguy45; 12-08-10 at 07:13 AM.
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Old 12-10-10, 09:16 AM
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Repair Cost

We had a technician come in and look at it. It turns out the furnace's circuit board needs to be replaced at a cost of about $685 installed. Does that sound right?
 
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Old 12-10-10, 09:30 AM
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That's probably not out of line depending on where you live. I'll bet the board probably only costs about $150-200, but they'll have to mark it up. You might even be able to buy it and replace it yourself.

What if it's not the real problem, though? Then you'll have no recourse to call them back or get a refund.
 
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Old 12-10-10, 09:55 AM
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Repair Cost

Is it a relatively easy job for someone with no particular knowledge of furnaces? The prospect of saving 500 bucks makes it pretty tempting to try, but I don't want to get in over my head.
 
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Old 12-10-10, 10:06 AM
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That, I can't really tell you, not familiar with your unit. Not a HVAC Pro...but I've worked in electronics and fixing things all my life, so I would probably be tempted. Matter of fact...I fixed my own at my last house...even after a "repairman" told me it was something completely different.

Let one of the Experts weigh in.

Oh...did they say a specific board number or a least point it out? And what is the complete model, age, and serial number of your furnace...the G20 is a family, but there are variations I believe.
 
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Old 12-10-10, 11:06 AM
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Model Number

The model number is C23-41WFC-1. the serial number is 6097M11943.
 
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Old 12-10-10, 06:46 PM
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try Best Buy Heating and Air Conditoning Parts Online! for parts pricing on the boards.the heating side call for fan comes from the furnace not the stat and is LOW for heating and HI for cooling..that comes thru the stat in the summer..WHY..it takes air longer to absorb heat then loose it.check the wiring diagram on the motor housing you should have a minimum of 3 speed colors hi/med/lo ...even 4 maybe a med/hi...if slip stake-ons just slip the lo wire out and insert any other if the motor run in the heat call cycle the LO winding is shot use MRD for now and check Grainger Industrial Supply for exact replacement they welcome home owners...cash credit..but definitly check those board prices you will go try build one before paying a contractor...and you'll feel great doing it yourself always all power off at the furnace
 
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