HVACopediaGoodman · Furnace troubleshooting
Measure inlet gas supply pressure
What is going on
Measure supply pressure with burners firing and other gas appliances on the same line running. Supply must fall within the rating plate range.
Likely causes
- Line pressure out of range
- Undersized gas piping
- Regulator fault
Check in this order
- Shut off electrical power and the manual gas shutoff valve.
- Remove the burner compartment door to reach the gas valve.
- Install a hose fitting at the gas valve inlet tap or the gas piping drip leg.
- Connect a calibrated water manometer or gas pressure gauge.
- Turn on gas and power, and run the furnace and other gas appliances on the line.
- Read supply pressure with burners firing and compare to the table.
- Turn off unneeded appliances, shut off gas and disconnect the manometer.
- Reinstall the plug, turn gas back on and check for leaks.
- Reinstall the burner door and verify operation.
Applies to: Inlet gas supply pressure at gas valve
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 manual, p. 51. 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.