Daikin Altherma fault J3-00

What it means

Discharge pipe thermistor input is out of range, causing the unit to stop operating.

Likely causes

1. Faulty discharge pipe thermistor or connector fault
2. Faulty main PCB
3. Deviation of thermistor (higher temperature measured than actual).
4. Faulty room thermistor
5. Bad contact between sensor and pipe
6. Deviation of outlet water after backup heater thermistor (lower temperature measured than actual)
7. Deviation of thermistor (lower temperature measured than actual)
8. Incorrect refrigerant charge
9. Faulty expansion valve control
10. Faulty suction thermistor
11. Blockages in refrigerant circuit
12. Domestic hot water tank thermistor measures a higher temperature than actual (component failure)

Where to start

1. Perform a check of the discharge pipe thermistor
2. Perform a check of the main PCB
3. Measure the room temperature and compare to the room temperature shown on the user interface (remote controller)