Hi I have a York furnace gas :
The problem in the furnace goes through it's cycle as normal it seems. But the gas valve doesn't open ( no clicking, no flow), so it recycles 2 times and shuts down a I get the code lockout- check furnace. the first time it did this I checked all the connections (electric) all seemed clean and ok, I checked the rollout relays none were open I jumped the 3 relays on the top of the flame inlet, and the furnace started. I figured that was the problem, so I bought new ones to replace them in the mean time the furnace stopped working again. So it wasn't the relays, but now I have them. So I noticed that the furnace is sporadic, it starts and doesn't at will. I had a furnace tech (air Tech of NJ) come to check it out he said it could be the flame sensor, or the vacuum switch or the manifold is broken. Well I looked at the manifold it looks great, it is a stamped steel type. On the old furnace which this one replaced, it had a cracked cast iron manifold. Anyway replacing the flame sensor doesn't seem like it would be causing the problem, doesn't that sensor detect flame when the unit is running and close the gas valve if the flame goes out before the heating cycle is done? The flame doesn't lite because gas isn't flowing, the vacuum switch I don't know what that does, anyway he said he checked all the connections and replaced the flame sensor and the unit has been running good for the last 2 weeks till last night.
At around 6pm when the T-stat called for heat the unit cycled and the fan came on with no heat. I called the service guy and waited for a call back. anyway through out the night I heard the unit come on a few times and the house was warm. this mourning the heat came up and the next time nothing. and still nothing. I looked at the unit and it doesn't look like the repairman ever replaced the flame sensor because it is still dusty and the surrounding area looks like it was never touched. I don't know what he did the first time. I looked in the chimney and the metal exhaust pipe from the unit to the chimney and no obstructions.
I am selling the house and have insurance for the house and Air-tech is who the ins co sent. I don't know if they are the best, they really don't sound very convincing when they tell what they think is wrong. I like to be able to tell them what might be wrong.
Thanks for all and any of your help.