The solenoid coil that drives the valve may be burnt out or disconnected.

: Turn off the AC using the main power switch or circuit breaker. Leave it off for at least 10 minutes to clear the system's memory before turning it back on.

Disconnect the power at the main isolator switch or unplug the unit. Wait at least 5–10 minutes to allow the capacitors to discharge fully. Restore power and check if the code persists. Check Remote Wiring

If you have cleaned the filters, checked for obstructions, and reset the unit, but the 9C code persists, it is time to call a certified HVAC technician.

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