Display shows E2 and cooling or heating stops; fan may still run.

Safety: Unplug the unit before opening any panels. Sharp metal edges are present around the coil and chassis.

• Remove covers: Take off the rear or side panel (portable units) or front grille (window units) to expose the indoor evaporator coil (the cold finned coil).
• Locate the sensor: Find the small thermistor clipped or taped to the evaporator tubing or fins. It will have two thin wires leading back to the main PCB.
• Check mounting: Ensure the sensor is firmly attached to the coil surface. If it has fallen off, reattach it using aluminum tape or the original clip so it makes good thermal contact.
• Inspect wiring: Look for pinched, cut, or rubbed‑through wires, especially where they pass through metal openings. Repair minor insulation damage with electrical tape; replace the harness if conductors are broken.
• Connector check: Unplug the sensor connector from the PCB and re‑seat it. Inspect for corrosion or bent pins.
• Test the sensor: With a multimeter, measure resistance at room temperature. Compare to the ambient sensor if they are the same type; they should be in a similar range. A reading of 0 Ω or infinite resistance indicates a bad sensor.
• Replace sensor: Install a new Whynter evaporator temperature sensor / thermistor if the old one is defective. Secure it tightly to the coil.
• Board diagnosis: If a new sensor does not clear E2, the main control PCB may be defective and should be replaced by a professional.