Error code reference

Trane Furnace Error Code 3

1st stage pressure switch is stuck open (not closing).

First step from the service manual

Cycle power to the furnace and call for 1st stage heat; verify all wiring to pressure switch is correct per wiring diagram.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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1st stage pressure switch is stuck open (not

From Service Manual 469971, p.23:

1.Cycle power to the furnace and call for 1st stage heat; verify all wiring to pressure switch is correct per wiring diagram.

2.Measure line voltage at the power cord terminal block. Expected: 120 VAC (L1 to neutral) or 208 to 240 VAC between L1 and L2 under load.

3.Inspect the cord strain relief and terminal block screws for signs of arcing or heat discoloration. Loose connections here mimic an intermittent power failure to the control board.

Part W10911048

Power cord assembly

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First step from the service manual

Get the full diagnostic procedure for 3.

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