I have H64 error on my LA-MI heat pump. What does this mean?

Modified on Wed, 22 Feb 2023 at 10:00 AM

Applicable to models:  LA6MI, LA9MI, LA12MI, LA16MI


Issue:  Error code H64 shown on the display. No heat, compressor is stopped.  


What this means: H64 error is due to a refrigerant high pressure abnormality.

Until an engineer can attend, it should still be possible to use the electric backup. To enable the backup search for the guide "How to I switch on the backup on the LA-MI heat pump?" on the GDHV Help Centre.

Action: Engineer will need to investigate by following the flow diagram below.

Note that only F-GAS qualified engineers are legally allowed to work on the system if they are leak checking or changing refrigerant components!

Malfunction Decision Conditions:

During operation of defrosting and heating, when the outdoor high pressure sensor output signal is 0Vdc or 5Vdc.


Malfunction Caused:

1 Faulty connector connection.

2 Faulty sensor.

3 Faulty outdoor unit PCB (main).

Abnormality Judgment:

Continue 4 times in 20 minutes.


Location of connector & sensor on LA6MI / LA9MI Refrigerant PCB:


Location of connector & sensor on LA12MI / LA16MI Refrigerant PCB:

Possible parts required depending on engineers diagnosis:

• High Pressure Sensor
LA6MI / LA9MI / LA12MI / LA16MI part: X-2511012

• Main Refrigerant PCB (part number depends on model of heat pump)
LA6MI part: X-2511024
LA9MI part: X-2511038
LA12MI part: X-2511044
LA16MI part: X-2511057

Require additional help? Please follow link below


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