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Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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i have a duncane brand direct vent forced air furnace that

Resolved Question:

i have a duncane brand direct vent forced air furnace that has stopped trying to work (heat) no matter how high you turn the thermostat. the green light on the Honeywell SV9520H 8042 SmartValve repeats a pattern where it blinks twice then waits a while and blinks twice more endlessly. does this mean anything in particular? thanks.
Submitted: 7 years ago.
Category: HVAC
Expert:  Matthew replied 7 years ago.
Yeah that means the pressure switch is stuck closed. Find the pressure switch (round cylinder with 2 wires and a rubber hose coming off of it) pull one of the wires off and see if the furnace starts up. If it does this switch is stuck closed and you need a new one. If you want heat you have to unhook one wire and let the inducer motor start up then hook the wire back up and it will heat. Once the heat call is over it will not start up the next time the thermostat calls and you will have to do this all over again.
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Expert:  Matthew replied 7 years ago.
Do not leave it like this though you must have the switch to prove that the exhaust is running, and if the exhaust isn't running and the heat is on it could be very harmfull to you and your equipment.