Lennox furnace G1204 137-3


Old 07-31-19, 02:28 PM
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Lennox furnace G1204 137-3

I need a wiring diagram for my furnace. Modle G1204 -137-3 it is an upflow furnace
LP gas with a AC coil on top. With the thermostat set for FAN ON or AUTO the blower motor runs on and off at 30 second intervals when the AC or HEAT is on. I think one of the LIMIT or SAFETY controls in the furnace is causing the problem.
Any help will be appreciated.
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Old 07-31-19, 05:33 PM
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Are you using a Nest thermostat?
Use your meter to check the call for blower operation on the terminal block.
Old 08-01-19, 07:43 PM
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Check the motor for running hot. You may have a bad capacitor and the motor is shutting down on thermal overload. The wiring diagram for the furnace should be on the back of the blower door.

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