Thermostat calls for cooling, but only the indoor blower runs; outdoor unit does not start.

Safety: Turn off power to both indoor and outdoor units before opening panels. High voltage is present in the outdoor unit.

• Step 1 – Check thermostat wiring: Confirm the cooling call wire is on Y/Y1 at the thermostat and air handler control board.
• Step 2 – Inspect safety switches: Look for a condensate float switch or pan switch wired in series with the Y circuit. If the drain pan is full, clear the blockage and reset the switch.
• Step 3 – Check fuse: Inspect the low‑voltage fuse on the air handler control board and replace if blown. If it blows again, there is a short that needs professional diagnosis.
• Step 4 – Test contactor coil: With a call for cooling and power on, a technician can measure 24 VAC at the outdoor unit contactor coil. If present but the contactor does not pull in, replace the contactor.
• Step 5 – Technician service: If no 24 VAC reaches the outdoor unit, have a technician trace the Y circuit and repair wiring or control board issues.