Y002
GLAS
Shorted Y (Cool Call) Circuit
Thermostat displays Y002 and the air conditioner runs when GLAS is not calling for cooling, or continues running after setpoint is reached.
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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
Y wire shorted to R in thermostat cable, Miswiring at furnace/air‑handler control board, Stuck closed Y relay on GLAS main board, Moisture or debris bridging Y and R terminals
How to Fix / Troubleshooting
Safety warning: Turn off power to HVAC equipment at the breakers before touching wiring.
- Step 1 – Inspect GLAS wall plate: Remove the thermostat and ensure no bare copper from the Y wire is touching R or other terminals.
- Step 2 – Inspect furnace/air‑handler terminals: Confirm Y and R wires are properly separated and no strands are bridging.
- Step 3 – Cable check: Look for crushed or water‑damaged sections of thermostat cable that could cause a short between Y and R.
- Step 4 – Isolate GLAS: Disconnect the Y wire from the GLAS wall plate and restore power. If the AC still runs, the short is in the wiring or control board. If it stops, reconnect and test; if the problem only occurs with GLAS connected, the Y relay is likely stuck closed.
- Step 5 – Replace faulty component: Repair/replace damaged cable or control board as needed. Replace GLAS if its Y relay is defective.
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Repair Difficulty
Hard
4/5
Required Part
Thermostat Cable or GLAS Main Control Board (Y Cool Relay)
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