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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have an automatic pilot light that wont light. When the

Customer Question

I have an automatic pilot light that wont light. When the furnace is turned on, it goes through the cycle 5 or 6 times and then the blower kicks on, but no fire. i am getting a one blink code which ive come to understand indicates a lock out. i cleaned the flame sensor to no avail. what are other common problems that would cause this?
Submitted: 7 years ago.
Category: HVAC
Expert:  Wes replied 7 years ago.
Hello, is the small induction fan running? graphic
Customer: replied 7 years ago.
yes. it turns on with the furnace. a couple weeks ago we had a problem with it. the furnace wouldnt turn on but it turned out that the exhaust was blocked outside the house by a garbage bag. i got a three blink code during that incident, but like i said, this time im only getting one blink.
Expert:  Wes replied 7 years ago.

Ok the first thing you need to check is the tube connected from the inducer fan to the pressure switch. Make sure the tube is clean an not cracked or broken you can pull the tube off the pressure switch with the fan running and you should feel suction if thats good you want to check the pressure switch itself to make sure the contacts are closing

Edited by Charles on 1/11/2010 at 3:20 PM EST
Customer: replied 7 years ago.
there is suction, and the tube is in good condition. what is the best method for testing the switch? it has been my understanding that you can temporarily bypass the switch to see if the furnace starts. is this true?
Expert:  Wes replied 7 years ago.

yes this can be done by connecting the two wires connected to the pressure switch together and then starting the heat cycle. Another way to check the switch is with an ohm meter. disconnect the wires to the pressure switch when the inducer fan starts you should have a path between the two contacts on the pressure switch. Let me know how this checks out

Customer: replied 7 years ago.
Unfortunately, bypassing the pressure switch didnt work. im still getting same problem, same blink code.
Customer: replied 7 years ago.
Is there any other problems associated with that blink code? possibly related to the ignitor?
Expert:  Wes replied 7 years ago.
I'm not sure about the blink code I'm trying to find some information on your unit but I'm going through the steps I'd take to find out why the burner is not lighting. The next step is to check if your getting 24 volts to the gas valve and yes this could be a problem with the igniter the gas valve or the board.