Thermostat shows O/B01 and heat pump reversing valve does not switch correctly; system may cool when calling for heat or heat when calling for cool.

Safety warning: Turn off power to the air‑handler and outdoor heat pump at the breakers before opening panels.

• Step 1 – Verify system type: In GLAS settings, confirm the system is configured as a heat pump and that the O/B terminal is enabled.
• Step 2 – Check O/B polarity: Determine whether your heat pump uses O (energize in cool) or B (energize in heat). Set the GLAS O/B option accordingly.
• Step 3 – Inspect wiring: At the GLAS wall plate and at the air‑handler/heat pump control board, verify the O/B wire is connected to the correct terminal and is secure.
• Step 4 – Continuity test: With power off, disconnect O/B at both ends and test continuity. Replace cable if open.
• Step 5 – Functional test: With power on and caution, manually jumper R to O/B at the air‑handler board to see if the reversing valve energizes (you should hear a click at the outdoor unit). If it does, but GLAS cannot control it, suspect the O/B relay on GLAS.
• Step 6 – Replace thermostat: If wiring and configuration are correct and the system responds to a manual jumper but not to GLAS, replace the thermostat.