I have a Trane XR90 furnace that is flashing a pressure switch error code. I have cleaned every nipple and hose attached to the pressure switch housing, and every connecting end. I have ensured all water in condensate pipes has cleared. I have ensured there are no exhaust or intake blockages. My inducer fan seems to me to be working fine.

Gently blowing into each hose to the pressure switch housing results in a click, but then I hear a second click back when i stop blowing.

My ohm meter reads infinite on the pressure switch contacts, but if I test while blowing into a hose attached to the pressure switch housing, the ohm meter reads zero (click), and when I stop blowing, it returns to infinite (another click).

I tried to test the switch using a voltmeter as well, and I can't get a consistent voltage reading (the multimeter jumps all over the place...not sure if I'm using it correctly).

I tried jumping the pressure switch and calling for heat, and the furnace kicked in, however, when the thermostat stopped calling for heat when the desired temperature was reached in the house, the furnace stopped (of course), and the pressure switch error code returned.

The other thing that resulted in the furnace kicking in was pinching the hose that comes from the pressure switch housing and goes to the burner cover at the burner cover end.

How can I tell if this is a faulty pressure switch or a different problem? I don't want to buy a new switch and then discover it was not the problem. It seems to me the switch is working if with the switch on the circuit I could get the furnace to ignite by altering the pressure by pinching one hose.

 

Welcome to the forums.

Leave the model number for your XR-90 furnace. The model can usually be found on an ID plate on the sides near the burner.

The pressure switches are very accurate and rarely go bad. You said you pinched off the line and the switch activated. That's telling me that the pressure switch is getting too much pressure from something not properly opened/or clogged.

 

Thanks much for the response. The model # is TUX1D120A9601AB.

Your rationale makes sense. I can't find any blockage, though. Any thoughts on where it might be? I was able to get the burners to kick in and the louder fan to go when I pulled off the tube that goes from the pressure switch housing to a nipple next to the gas control switch (at the gas line end, not the pressure switch end) and left it open to air.

 

This is for anyone experiencing pressure sensor / limit switch issues with the XR series Trane furnaces - - - I went the end of one winter seasons and the beginning of the next trying to resolve this issue..... then three service calls, a limit sensor, a pressure switch, a blower motor; and, about $400 later the problem still existed.

So, I then I donned my own Sherlock Holmes hat and rehashed what the previous three tech's had stated and supposedly fixed and figured out that the only damn thing wrong were the freak'n filters were dirty/or the wrong micron factor.

Since I replaced my filters with a maximum MERV Rating 8 filter I've not had a problem.

Not once did a tech say let's try chancing the filters..... hmmmm!

 

I am having a similar problem with pressure switch BA 20106 (also referred to as Honeywell SWT2357). It is a dual pressure switch module. The difference for me is that I do not get a change of state when I blow into the housing. Pretty sure the switch module is bad. I plan to jumper out the switches and see if the unit runs. If your unit runs when you jumper the switch, it's a good bet the switch or the lines running to it are the problem.