Unit stops, may run briefly then shut down, E3 displayed on indoor unit

Safety first: Turn OFF power at the breaker before removing covers.

Steps:

• Access evaporator coil: Open the front panel, remove filters, and remove the plastic louver/grille (if required) to expose the evaporator coil.
• Locate the coil sensor: Find the thermistor clipped to the evaporator fins or inserted into a small pocket on the coil. It will have thin wires leading back to the PCB.
• Check mounting: Ensure the sensor is firmly clipped or inserted in its designated position. A loose sensor can cause incorrect readings and E3 errors.
• Inspect wiring: Follow the wires to the PCB and verify the connector is fully seated. Look for any signs of damage or corrosion.
• Clean the coil: If the coil is heavily iced or dirty, allow ice to melt completely (leave unit OFF for several hours) and clean the coil with a soft brush and approved coil cleaner. Do not bend fins.
• Test again: Restore power and run the unit. If E3 reappears quickly, the thermistor is likely defective and should be replaced.

Warning: Do not poke sharp objects into the coil; puncturing the refrigerant circuit is dangerous and expensive to repair.