U4 (5110) - Heat sink temperature thermistor open/short

What does U4 (5110) mean?

A fault (open circuit or short circuit) has been detected in the heat sink temperature thermistor (TH8) of the Mitsubishi Electric PUMY Air Conditioner. The system will stop operating.

• Faulty thermistor (sensor) component
• Loose or damaged wiring connection to the thermistor
• Corrosion or physical damage to the thermistor or its leads

Click steps to track your progress.

1. 1

   Note the error code displayed on the remote controller or outdoor unit.

2. 2

   Power off the Mitsubishi Electric PUMY Air Conditioner system at the main electrical breaker.

3. 3

   Wait for at least 30 seconds, then restore power to the system.

4. 4

   If the error persists, contact a qualified service technician to check the thermistor and its wiring.