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Lennox Furnace G23Q3/4 Failure to Heat

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Username: Hondo

Post Number: 1
Registered: 01-2015

Votes: 1 (Vote!)

Posted on Saturday, January 10, 2015 - 11:50 am:   Edit Post Delete Post View Post/Check IP    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I have a Lennox G23Q3/4 furnace that fails to heat, when the thermostat is calling for heat. If your at the furnace and turn the power Off and then ON, you can hear a click and nothing else. What should I check first??
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Username: Techsup

Post Number: 45
Registered: 02-2011

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Posted on Tuesday, January 20, 2015 - 04:02 pm:   Edit Post Delete Post View Post/Check IP    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

First check the LED on the Ignition Module. This LED should be lit while lighting the pilot etc., if the LED isn't lit and the thermostat is calling for heat, this means a failure is detected or no power.

Since there is no pilot ignition, I would say the LED is not lit. At this point we need to consider the click your hear when power to the furnace is turned on. Experience says this would be a relay closing. What it means is power is getting to the relay coil and not to the Ignition Module, etc..

Checking the electrical diagram for this furnace, it shows that power passes thru relay contacts going to the Ignition Module, Blowers and the ACC. The relays are located on the BCC Board, and in all likely hood one or more of the contacts has become pitted and burned over time and no longer makes good contact. This would be especially true if this is the original BCC Board. You can check this by measuring the voltage between N and CAB on the BCC Board, when calling for heat. This voltage should be 120 volts AC. If you have no voltage, contacts bad and change BCC Board. If you have voltage, the combustion blower should be running, if not check it.

The part# for the BCC Board is 48K98 BCC3, the current replacement.

This is really a job for the professional I would suggest, if you have any doughts making the repairs, call a Heating and Cooling professional.

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