Indoor unit blows warm air in cooling mode; outdoor unit not running

Safety first: Turn OFF power to the indoor unit before removing thermostat or access panels.

• Step 1 – Thermostat settings: Confirm thermostat is set to COOL and temperature is below room temperature. Ensure system is not in FAN ONLY mode.
• Step 2 – Check batteries: Replace thermostat batteries if applicable.
• Step 3 – Inspect wiring at thermostat: Remove thermostat and verify wires are firmly attached to R, C (if used), Y, G, and O/B (heat pump) as appropriate.
• Step 4 – Indoor board fuse: Check the low-voltage fuse on the indoor control board and replace if blown.
• Step 5 – Bypass test (qualified persons only): Temporarily jumper R to Y and G at the indoor board to see if the outdoor unit and blower start. If they do, the thermostat or its wiring is faulty.