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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22001
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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combustion blower run continuously on my lennox furnace. This

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combustion blower run continuously on my lennox furnace. This causes the vacume switch to remain shut and furnace will not start when the thermostat cause for heat. The furnace will start after i disconect the vacume tube on the blower and re-connect it. I assume it is a stuck relay switch on one of the boards. Is the combustion blower controlled by another relay? Thank you

That relay is on the main board. Even if it unsticks, it will stick again.

You will need to replace board.


here is service manual -


Customer: replied 6 years ago.
do you have board number that i need to order and can you recomend a company i can order the part from online? Thank you
BillyHvac and other HVAC Specialists are ready to help you
Customer: replied 6 years ago.
thank you for your help, Daniel Berger