Outside Air Temperature Sensor (ThOA) Defective

What does E38 mean?

The outdoor ambient air temperature sensor (ThOA) is defective (resistance is open circuit) or has a poor connection to the outdoor unit PCB. This impacts the system's ability to adjust operation based on ambient conditions, affecting efficiency.

1. 1

   Measure the resistance of the ThOA sensor at its leads — compare to a resistance-temperature chart if available.

2. 2

   Inspect the ThOA sensor's connector on the outdoor unit PCB — verify it is securely seated and free from corrosion.

3. 3

   Check for damage to the sensor wiring between the sensor and the PCB using a multimeter for continuity.