Appliance Diagnostic

Carrier Furnace Code 31 - High Pressure Switch Did Not Close

Code 31 signals that the furnace draft inducer motor ran, but the pressure switch failed to sense proper negative draft pressure.

What Caused This Error?

The control system reports 31 when the monitored condition described by the error code is outside the expected operating range. In this case, the most likely trigger is blocked pvc vent exhaust or fresh air intake pipe. Other common contributors include cracked or disconnected pressure switch silicone tubing and failed inducer blower assembly.

Step-by-Step Diagnostic Check

  1. Check exterior PVC flue termination pipes for bird nests, ice, or debris.
  2. Clear condensate drain lines and trap of standing water.
  3. Inspect clear pressure tube for cracks, moisture drops, or loose ports.
  4. Disconnect electrical power before opening panels. Replace draft inducer pressure switch.
Most Likely Replacement Part

Furnace Pressure Switch Assembly

OEM Part #: MODEL-SPECIFIC

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