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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Trane XV90 - Noticed only blowing cool air. No error codes

Customer Question

Trane XV90 - Noticed only blowing cool air. No error codes present. Checked ignitor and no glow. Removed ignitor to check for cracks but seems ok. Replaced the ignitor anyways and still no luck.
Submitted: 5 months ago.
Category: HVAC
Expert:  Phil replied 5 months ago.

Hello, is there a red LED glowing or blinking steady (no error code) on the printed circuit board? Does the inducer fan run?

Customer: replied 5 months ago.
The red light blinks every 20 seconds or so which I believe is the normal operation. The inducer fan starts up but that seems to be the end of the cycle. No further clicks, etc. Then the blower ramps up and only pushes out cool air.
Expert:  Phil replied 5 months ago.

Thanks, locate the pressure switch, its round, is near the inducer fan, and has one or two 1/4" black rubber tubes and two wire terminals..

then cycle the thermostat again, and when the inducer fan starts, and runs for 3 seconds of so, fit a jumper wire between the two terminals... if the furnace now runs we need to clean or replace the pressure switch.

Customer: replied 5 months ago.
I see two of what I believe you are talking about. See picture. They both appear to have two wires going in with the top one having a double yellow wire going into the same terminal and then a jumper wire down the the bottom one. Which one and should I be trying to fit a piece of wire behind these existing wires in the wire nut? Does it matter what type of wire or just whatever I may have lying around? Thanks.
Expert:  Phil replied 5 months ago.

Thanks, jumper the bottom pressure switch first, the one rated at 1.25" water column,

The other switch closes when the furnace goes to high stage heat and the gas valve goes to high stage, it closes at 2.25" wc.... for now however just jumper the bottom one, you can use a paper clip wire its only 24 volts

Customer: replied 5 months ago.
Ok, I put a jumper wire between the yellow and orange wires on the bottom switch and no luck. Same result. As a side note, the wait time is 5-10 minutes when starting the cycle over. Not sure if that's relevant but seemed longer than I remember.
Expert:  Phil replied 5 months ago.

Hello again, make sure that you place the jumper *3 to 10 seconds after the inducer fan starts.. not before the inducer fan starts.

so far, assuming that you did the jumper correctly, symptoms point to a bad printed circuit card,

I am off to bed now, I will pick your response up in the morning

Customer: replied 5 months ago.
I will retry the jumper process again to make sure I was doing it right. It is a little difficult to fit the wire in behind the existing wires to make the connection.
Expert:  Phil replied 5 months ago.

The existing spade connectors press onto the switch, you can slide them away from the switch by 1/8" or so in order to enable a better jumper connection