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Old 11-12-2012, 10:55 PM   #1
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Lennox G20R wont start


I have a Lennox G20R whisper heat furnace. It is failing to turn on.

I checked the fuse (the fustat fuse and the in-panel fuse). They are both good.
I checked to see if there is 24VAC between R&C - I measure 0V.
There is no clicking or sound when i turn on the unit. The damper door does not even open.

I recently changed the batteries on the controller unit and made sure the unit was working - that was about 3 weeks back (a regular yearly maintenance). The furnace worked after I replaced the batteries.

Any guidance here is appreciated.

Thanks,

-L

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Old 11-12-2012, 11:07 PM   #2
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Lennox G20R wont start


Confirm supply voltage..Does the thermostat have a fan on switch or do you have a meter to confirm supply voltage?

Remove the stat wire in the furnace connected to "R". Put a jumper between R & W to bypass the thermostat circuit.

If you have supply voltage and have jumpered the stat circuit..is the motor that operates the vent door receiving 24V?

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Old 11-13-2012, 12:09 AM   #3
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Lennox G20R wont start


I have a DMM to measure the voltage.

Thermostat has a switch.

I jumpered the stat wires as mentioned. Can you help me on how to check if the motor is receiving 24 VAC? I do not see leads at the motor.

Thanks,
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Old 11-13-2012, 12:23 AM   #4
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Lennox G20R wont start


Did the thermostat fan switch turn on your furnace blower fan?
or
Do you know if the furnace is getting 120V?
I am not sure from your posts if you've measured any power, be it 24V or 120V in the furnace.

Last edited by how; 11-13-2012 at 12:45 AM.
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Old 11-13-2012, 06:24 AM   #5
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Lennox G20R wont start


door has to open to 1st before ignition...check for 24 volts to motor on door ...ben sr
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Old 11-13-2012, 09:20 AM   #6
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Lennox G20R wont start


Thanks Ben Sr.

I checked for 24v between R&C terminals. I'm measuring 0. How do I check at the door motor?

Regards,
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Old 11-13-2012, 01:02 PM   #7
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Lennox G20R wont start


Quote:
Originally Posted by lucky66 View Post
Thanks Ben Sr.

I checked for 24v between R&C terminals. I'm measuring 0. How do I check at the door motor?

Regards,
check your transformer 1 st...120 in on blk & white...24 volt out ...ben sr
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Old 11-13-2012, 11:19 PM   #8
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Lennox G20R wont start


Checked both - I measure 0V at both locations.

I see a black spot behind the control board. I fear that something could have caused this to burn. Any advice on this?

As insurance, I have ordered a new control board.

Appreciate inouts.
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Old 11-14-2012, 06:21 PM   #9
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Lennox G20R wont start


No voltage means the fuse/breaker is blown. The burned out control board would be why.
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Old 11-14-2012, 06:25 PM   #10
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Lennox G20R wont start


AHH the good ole BCC board. Changed many of them and they get pretty roasted on the back when the fan relay blows.

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