Carrier / Bryant / Payne · Furnace error code

31Pressure switch did not close or reopened

Cross-checked High-voltage / caution

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Related diagnostic guides

Component test · Furnace

How to test a gas furnace draft pressure switch (electrical and draft checks only)

The pressure switch proves the inducer is pulling enough draft before ignition is allowed. Test it with a meter (24 V across it) and a manometer against the set point printed on the switch. Gas valve, gas pressure and burner work are not covered: refer those to a licensed gas technician.

5 steps ~30 minadvanced

Guide · Furnace

Pressure switch open / inducer problems

The pressure switch proves the inducer is moving combustion gases. It stays open when the vent/intake is blocked, the hose or port is plugged, the condensate trap backs up, or the inducer is weak.

5 steps ~45 minmoderate

Guide · Furnace

Furnace runs no heat (blower only or nothing)

Start with the board LED code, then work the call path: thermostat, 24 V, safeties, inducer, ignition, flame proving. Most no-heat calls end at a filter, a flame sensor, a pressure switch issue or gas being off.

5 steps ~45 minmoderate