HVACopediaGoodman · Furnace troubleshooting
High stage pressure switch stuck closed at start of heating
What is going on
The furnace runs fine on low stage but won't go to high. The high stage pressure switch is reading closed at the start of the cycle when it should be open, so the board won't bring on high fire.
Likely causes
- High stage pressure switch contacts sticking
- Shorts in pressure switch circuit wiring
Check in this order
- Turn power off before repair.
- Disconnect the switch leads and check across the switch with a meter. It should be open with the inducer off.
- Replace the high stage pressure switch with the correct part if the contacts are stuck.
- Repair the short in the wiring if the switch itself checks out.
- Restore power and run the furnace on both stages.
Applies to: 34.5 in chassis gas furnaces
More furnace guides
- Airflow lower than demanded, furnace runs on low stage when high stage is expected
- Alternate combustion air opening (upflow or horizontal)
- Alternate vent/flue location (upflow or horizontal left)
- Annual inspection checklist
- Auxiliary limit control (location and purpose)
- Auxiliary limit switch open (blower compartment)
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Source: Goodman GMVC96 Service and Troubleshooting, p. 61. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.