Outdoor Fan Motor; Low Pressure Switch; Way Valve; High Pressure Switch - Haier 2U18MS2VHB Service Manual

Outdoor Fan Motor

The Outdoor Fan Motor is a variable speed motor. The motor
is energized via a connection plug on the ECU. The motor
is powered by line voltage from the ECU. The motor has a
PWM circuit that feeds back voltage to the ECU. The ECU will
control the speed of the motor by a DC voltage applied to the
yellow wire of the connection plug. The feedback PWM signal
from the fan motor is applied to the ECU via the blue wire on
the connection plug.

Low Pressure Switch

The system has a Low Pressure Switch that will shut down
system operation if abnormally low refrigeration circuit
pressure is detected. This switch is connected to the ECU via
an electrical plug. During normal operation this switch will be
closed.
If the switch were to open during a call for cooling or heating
mode operation, the system will shut off the compressor
and display an error code. If the pressure rises to re-close
the switch, the compressor will re-start and continue on with
normal operation. Multiple cycles of opening and closing the
switch will cause the system to lock out and display an Error
Code 43.
Causes of low refrigerant pressure include leaks,
undercharging, restrictions, EEV failure and cold room air
temperatures/dirty indoor coils/restricted airflow at indoor
unit.
Components

4 Way Valve

The 4 Way Valve is energized during heating mode operation.
The valve is energized with 230 volts via a connection plug on
the ECU. When energized, the valve directs the compressor
hot gas to the indoor coil.
During Cooling mode and Defrost mode operation, the valve
is de-energized. When de-energized, the valve will direct the
compressor hot gas to the outdoor coil.

High Pressure Switch

The system has a High Pressure Switch that will shut down
system operation if abnormally high refrigeration circuit
pressure is detected. This switch is connected to the ECU via
an electrical plug. During normal operation this switch will be
closed.
If the switch were to open during a call for cooling or heating
mode operation, the system will shut off the compressor and
display an error code. If the pressure drops to re-close the
switch, the compressor will re-start and continue on with
normal operation. Multiple cycles of opening and closing the
switch will cause the system to lock out and display an Error
Code 42.
Causes of high refrigerant pressure include overcharging,
restrictions, EEV failure, and dirty outdoor coil.
OUTDOOR TECHNICAL OVERVIEW
B-5