Fault codes covered
64-44
Applies to HP only. EXV-H is required to control superheat in heating mode. Each time power is applied to the unit, the EXV-H will operate to a known position as the valve does not have the capability to feedback actual position. The PCM software must know the starting point and then count when stepper motor is pulsed. At the end of each cycle the valve will close to help maintain pressure differential and optimize cyclic efficiency. HP units will not operate if this fault is active because the valve position at time of failure is unknown.
This code occurs when the PCM determines the EXV power supply is drawing excessive current. The most likely cause of this fault is the wire attached to pin 1 of EXV-H connector being shorted to ground. Inspection of the wire harness and plug should be performed, as well as using multimeter to confirm “short to ground” continuity. If nothing is found, replace coil and harness assembly.
Source: ACHPVSR454-02SM troubleshooting pages.