HVACopediaGoodman · Furnace troubleshooting
Grounding fault
What is going on
The furnace doesn't run and the board is showing a grounding error. The control needs a solid ground and a good neutral before it will light anything, and a loose or poor neutral is the usual cause.
Likely causes
- Poor neutral connection
- Loose or corroded ground at the furnace or at the panel
Check in this order
- Turn power off before service.
- Verify the neutral wire connection to the furnace and its continuity to the ground source.
- Tighten and clean the neutral and ground terminals at the furnace and at the panel.
- Restore power and check for about 120 V between hot and neutral, with very little voltage between neutral and ground.
- Don't use the gas line as a ground.
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. 62. 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.