Indoor control board LED flashes L3 and the compressor cycles off on safety

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.

Possible Causes

Repeated high- or low-pressure switch trips, Blocked airflow across coils, Refrigerant charge problems, Faulty pressure switch on American Standard condensing unit

How to Fix / Troubleshooting

Safety first: Turn off power to both indoor and outdoor units before inspection.

Check filters and vents: Replace dirty air filters and ensure all supply and return vents are open.
Clean coils: Clean both indoor evaporator and outdoor condenser coils if accessible. Dirty coils can cause abnormal pressures.
Reset lockout: Turn off power for 5–10 minutes to clear the lockout. Restore power and observe operation.
Professional service: If L3 returns, a technician should check refrigerant pressures and test the pressure switches and wiring.

Repair Difficulty

Hard 4/5

Required Part

High-Pressure Switch

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