incarmel

Got 3-flash code for pressure switch problem on my trane xe90 system (~15 year old).
The inducer fan runs with normal sound. Can see the turning of fan.
Opened the front tube to pressure switch and saw water dripping out. Dirty brown rusty water also came out of the front hole on the pressure switch.
Opened the back tube to pressure switch. Can feel air coming out of this tube but don't know the pressure.
I suspect the pressure switch is dead.
Any suggestions for this issues?

Thanks.

Wuzzat?

Get the specs for the switch and simulate the setpoint pressure by using a column of water. You'll need some tubing from the hardware store, and a meter.

If it's like 0.05" WC [about 3/64"] you may want to put a drop of hand dishwashing liquid in the water. It breaks the surface tension so you get a more accurate reading.
Or you can slope the tubing which will amplify how visible this 3/64" is. A 10 degree slope will give you a 17/64" difference.

From Grainger, roughly half of their switches cost between $44 and $26.

kok328

clean the openings on the inducer motor where the tubes connect & check the exhaust pipe for wasps/bees nest looking for any blockage that may prevent the pressure switch from "making".

incarmel

My contractor just extended the exhaust pipe to ~9" tall. I assume it is clean inside.

The inducer motor/drain tube are also clear.

incarmel

Ordered a new switch and will arrive tomorrow. Will update.

Update:
My new pressure switch arrived.
Put it to replace the old one.
The furnace back to work.

Thank you guys for the help.