Branch Box LED 402 blinks 7 times & LED 403 is lit — Indoor Unit A, gas pipe thermistor error.

What does LED 402 (7) / LED 403 Lit mean?

LED 402 flashes seven times and LED 403 is lit, indicating an error with the gas pipe thermistor for Indoor Unit A.

• The thermistor for Indoor Unit A's gas pipe is open, shorted, or malfunctioning.
• Faulty wiring connection to the thermistor.

Click steps to track your progress.

1. 1

   Reset the power to Indoor Unit A and the branch box by cycling their circuit breakers.

2. 2

   If comfortable, power off the unit and check the connections of the gas pipe thermistor for Indoor Unit A for any visible damage or looseness.

3. 3

   If the problem continues, a technician should check the thermistor's resistance or the Indoor Unit A's PCB.