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I have a Lennox pulse 21 furnace. It will not turn on when I turn it to cool or heat. I checked the main computer module and the LED light is off. I had reset the furnace by using the switch next to the furnace, and this will not turn on the light. Is there anything else I need to check before I call a service tech to look at the main module? The switch to turn on and off the furnace with the removal of the bottom door may be bad. Is there anyway to check this?

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The switch you are talking about can be checked. Turn power off to unit. Disconnect wires on both terminals of this door switch. Next use a meter that will show Ohms or just connectivity to see if switch is closed when pressed all the way in. You could use a cheap meter from auto parts store to see if switchis good. You could remove switch and take to automotive parts store and they would actually check for you. If that device is good. Please follow wires from main power and see if there is a fuse before or on the main control board.. There will be a transformer that converts supply voltage to 24 or 28 volts and when turning power on that transformer will become warm and have a very small humming noise.. let me know what you find and if you need anything else.

Posted on Aug 29, 2010

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