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lucky66 11-12-2012 10:55 PM

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.



how 11-12-2012 11:07 PM

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 the motor that operates the vent door receiving 24V?

lucky66 11-13-2012 12:09 AM

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.


how 11-13-2012 12:23 AM

Did the thermostat fan switch turn on your furnace blower fan?
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.

ben's plumbing 11-13-2012 06:24 AM

door has to open to 1st before ignition...check for 24 volts to motor on door ...ben sr

lucky66 11-13-2012 09:20 AM

Thanks Ben Sr.

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


ben's plumbing 11-13-2012 01:02 PM


Originally Posted by lucky66 (Post 1051161)
Thanks Ben Sr.

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


check your transformer 1 st...120 in on blk & white...24 volt out ...ben sr

lucky66 11-13-2012 11:19 PM

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.

Marty S. 11-14-2012 06:21 PM

No voltage means the fuse/breaker is blown. The burned out control board would be why.

yuri 11-14-2012 06:25 PM

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

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