Daikin Altherma 3 H HT Diagnostics
Classification: HVAC & Boilers Equipment
Hardware operational fault codes, protection alarms, LED blink sequences, and step-by-step diagnostic fixes for the Daikin Altherma 3 H HT.
Indexed Fault Codes for Altherma 3 H HT
Step-by-step resolution manuals and root cause matrices
Water Flow Switch Interlock Failure
Error 7H-01 triggers when the hydro module Main PCB detects that the water flow switch contact remains open during circulation pump operation (interlock opened) or closed when the pump is idle, indicating insufficient hydronic flow (<12 L/min) or a defective flow sensor circuit.
Outdoor-Indoor Transmission Failure
Error U4-01 designates a serial communication loss between the outdoor hydro/inverter inverter PCB and the indoor hydro unit PCB. The system trips to protect the compressor from unmonitored operational states.
Inverter Instantaneous Overcurrent Fault
Error L5 indicates that the outdoor inverter printed circuit board (PCB) detected an instantaneous overcurrent trip on the compressor drive circuit via the current transformer (CT) or shunt resistors. The IPM shut down operation to prevent catastrophic semiconductor and compressor failure.
Outdoor DC Fan Motor Lock
Error E7 indicates that the outdoor unit inverter main PCB has detected a DC fan motor rotation failure, lock condition, or lack of Hall effect feedback signal while attempting to drive the fan.
Outdoor Fan Motor Locked Rotor
Error E7-01 indicates an outdoor DC fan motor overload or locked rotor condition. The inverter PCB detects zero Hall IC feedback pulses or excessive motor winding current during startup or operation, frequently triggered in sub-zero ambient temperatures by ice entrapment around the fan cowl or internal motor bearing seizure.
Inverter PCB Communication Fault
Internal serial communication loss between the outdoor main control PCB (A1P) and the compressor inverter driver PCB (A2P). The safety watchdog triggers an emergency lockout to protect the IPM and compressor.