Tempstar air conditioner indoor display shows E4 and cooling stops during operation

Safety first: Turn OFF power to the indoor unit before removing panels.

Steps to address airflow:

• 1. Replace or clean air filter: Install a new filter of the correct size and MERV rating recommended by Tempstar. Avoid overly restrictive filters.
• 2. Check blower operation: With panels back on and power restored, set the thermostat fan to ON. Verify that strong airflow is coming from supply vents. Weak or no airflow indicates a blower motor or capacitor issue.
• 3. Inspect evaporator coil: If accessible, visually inspect the coil for dirt buildup. A heavily clogged coil should be cleaned by a technician using proper coil cleaner.
• 4. Verify coil sensor placement: The evaporator temperature sensor (thermistor) should be firmly attached to the coil tubing. If it has fallen off, carefully reattach it using a clip or zip tie, ensuring good contact.
• 5. Thaw if frozen: If ice is present, turn cooling OFF and fan ON for several hours until all ice melts. Then restart and monitor.
• 6. If E4 persists: Low refrigerant or a faulty thermistor may be the cause. Contact an HVAC technician for further diagnosis.