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Old 09-11-2013, 11:25 AM   #1
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Lennox HVAC Circuit board problem

I have a Lennox central unit with a 24L8501 circuit board that is flashing alternating fast lights. When I bypass it the blower goes on. There is 120 V getting to the board. The compressor is working.the model is G26Q4/5-100-6. It looks like the board was wet at some point. My friend said replace the board. Is there anything else I can try before spending the money?

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Old 09-11-2013, 04:34 PM   #2
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Lennox HVAC Circuit board problem

Here is a link to the service manual for your unit: http://0190acd.netsolhost.com/manuals/G26_Series.pdf

If you look on page 12 it shows that alternating fast flashes is:

Improper main ground or
Line voltage below 75 volts
Broken ignitor
Open ignitor circuit

Here is another link that contains a schematic for your board (page 10):


If you look at the schematic on page 10 (bottom right) it shows the main grounding point. That is where I would start be inspecting the ground and making sure it is tight and not corroded. Turn off power to unit before tightening any wires or screws as a safety precaution!

Do you have a condensate drain safety switch that might be preventing blower from coming on?

Last edited by firedawgsatx; 09-11-2013 at 04:51 PM.
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lennox 24l8501

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