Branch Box LED 402 blinks 6 times & LED 404 is lit — Indoor Unit B, liquid pipe thermistor error.

What does LED 402 (6) / LED 404 Lit mean?

LED 402 flashes six times and LED 404 is lit, indicating an error with the liquid pipe thermistor for Indoor Unit B.

• The thermistor for Indoor Unit B's liquid 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 B and the branch box by cycling their circuit breakers.

2. 2

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

3. 3

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