G002
GLAS
Shorted G (Fan) Circuit
Thermostat displays G002 and the indoor blower fan runs continuously even when GLAS is set to Auto and no heating or cooling is active.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
G wire shorted to R in thermostat cable, Miswiring at furnace control board, Stuck closed G relay on GLAS main board, Control board fan relay stuck on
How to Fix / Troubleshooting
Safety warning: Turn off power to the furnace/air‑handler at the breaker before touching wiring.
- Step 1 – Check GLAS fan settings: Ensure the fan mode is set to Auto, not On or Circulate.
- Step 2 – Inspect GLAS wall plate: Remove the thermostat and verify no bare copper from the G wire is touching R or other terminals.
- Step 3 – Inspect furnace board: Confirm G and R wires are not bridged by stray strands or corrosion.
- Step 4 – Isolate GLAS: Disconnect the G wire from the GLAS wall plate and restore power. If the fan still runs, the issue is in the furnace control board or wiring. If it stops, reconnect and test; if the fan runs only with GLAS connected, the G relay is likely stuck closed.
- Step 5 – Replace faulty component: Repair/replace damaged cable or furnace control board as needed. Replace GLAS if its G relay is defective.
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Repair Difficulty
Hard
4/5
Required Part
Thermostat Cable, Furnace Control Board, or GLAS Main Control Board (G Fan Relay)
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