Frigidaire air conditioner displays E4 and may shut down or run only the fan.

Safety: Disconnect power before servicing. Avoid bending or puncturing the refrigerant coils.

Steps:

• 1. Let the unit thaw: If you see ice on the evaporator coil, turn the unit off and let it sit unplugged for several hours until all ice melts. Place towels to catch water.
• 2. Clean filter and coil: Remove and wash the air filter. Vacuum dust from the evaporator coil fins using a soft brush attachment. Restricted airflow can trigger E4.
• 3. Check sensor placement: Locate the frost/evaporator sensor clipped to the coil. Ensure it is firmly attached to the tubing and not hanging loose.
• 4. Inspect wiring: Look for damaged wires or loose connectors between the sensor and the control board. Reseat connectors.
• 5. Test sensor: With a multimeter, check resistance at room temperature and compare to spec. Replace the sensor if open, shorted, or out of range.
• 6. Verify fan operation: Ensure the indoor fan runs at all speeds. A failed fan motor can cause coil freeze and E4. If the fan does not run, diagnose the fan motor and capacitor.

When to call a pro: If E4 persists after sensor replacement and cleaning, or if the coil repeatedly ices up, there may be a refrigerant charge or metering issue that requires a licensed technician.