[briarrantilla]

This summer I had flooding in my basement. The furnace was damaged. The inducer fan and control board were replaced. It worked fine for several months.

It recently stopped working again. The error code is 3 flashing lights indicating pressure switch stuck open. When disconnecting the pressure switch hoses, water drained out. I removed the pressure switch and drained it. I also removed the inducer fan to check for problems.

While the pressure switch and inducer were removed, I took them to my father's house where he has better electrical tools. We were able to start and run the inducer by powering it directly. The pressure switch appears to be working properly.

I reassembled the parts, and no luck. I can get the error message to change from stuck open to stuck closed by applying suction. The inducer will still not start. I am unable to check if power is being sent to the inducer, but since I know the fan works, I am assuming it is not.

I've decided it must be the relay in the control board, but the entire board was recently replaced. I suppose it is still possible. I keep wanting to return to the pressure switch, since I know it had water in it... but I am told that the inducer should still fire first.

Can a bad pressure switch prevent the inducer from firing, or am I just getting that code because the inducer won't start?

I am new to the forum. Any advice would be appreciated. Thank you in advance.

 

[Bobplumb]

If installed correctly pressure switch should be in relay with the fan, so replacing that may be the answer

 

[beenthere]

Thr inducer must run in order for the pressure switch to close. So the pressure switch has nothing to do with the inducer not running.

 

[Jnaas2]

Post picture of wiring diagram

 

[throrope]

Our Lennox furnace has safety switches wired in series. All have to make contact for the thing to run. If you saw water damage, I suspect your safety switches are slowly giving up the ghost. I suggest you look at all before digging at a new control board that in my experience is often the last to fail. The safety that went on mine is on the back side of the blower and was a bugger to get at. I replaced all in that series for another twenty bucks just to take them out of the equation.