SERVICING
12
WARNING
Damage can occur to the glass embedded terminals if the
leads are not properly removed. This can result in terminal
and hot oil discharging.
WARNING
Disconnect power supply before servicing.
TESTING TEMPERATURE SENSORS AND EEV COIL
RESISTANCE
The AVZC ready heat pump models and AVPEC indoor
units are factory equipped with:
• (Ta) an outdoor air temperature sensor
• (Tm) an outdoor coil temperature sensor
• (TI) an outdoor liquid temperature sensor
• (Td) a discharge temperature sensor
• (Tb) a defrost temperature sensor
• (Tgi) an indoor gas temperature sensor
• (Tli) an indoor liquid temperature sensor
To check above sensors:
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or in-
stalling this unit. Multiple power sources may
be present. Failure to do so may cause proper-
ty damage, personal injury or death.
1. Disconnect power to the heat pump condensor.
2. Disconnect the sensor from the electric board.
3. Connect an ohmmeter across the sensor terminals.
The ohmmeter should read be the resistance shown
in the table THERMISTOR RESISTANCE AND
TEMPERATURE CHARACTERISTICS. Replace the
sensor if the sensor is open, shorted, or outside the
valid resistance range.
TESTING EEV COIL RESISTANCE
To check the resistance of the EEV coil, first disconnect
EEV cable from the Control board. Make measurements of
resistance between the connector pins, and then make sure
the resistance falls in the range of 40 to 50Ω.
TESTING REVERSING VALVE
CHECKING REVERSING VALVE AND SOLENOID
Reversing valve used in heat pumps could potentially leak
internally. Discharge gases can leak into the suction inside
the valve. Compound gages will give the same symptoms
as bad compressor valves or broken scroll flanks. The
temperature between true suction and the suction line after
the valve should not be greater than 4 degrees.
NOTE:
The
center tube is always the suction line and should be cold.
TROUBLESHOOTING THE REVERSING VALVE FOR
ELECTRICAL FAILURE
Place unit into the cooling mode. Test for 24 volts at the
solenoid. If there is no voltage present at coil, check the
control voltage. If voltage is present, loosen the nut on the
top of the coil. Remove the coil, there should be slight resis-
tance. If the slight resistance is felt, remove the coil. As you
remove the coil listen carefully, an audible click should be
detected. The clicking is due to the movement of the pilot
valve plunger. The absence of a clicking sound indicates
the plunger is stuck.
TROUBLESHOOTING MECHANICAL FAILURES ON A
REVERSING VALVE BY PRESSURE
Troubleshooting the reversing valve can be done by pres-
sure and touch. Raise the head pressure. In the cooling
mode block the fan exhaust. Once head pressure has been
raised, cycle between cooling and heating and see if the
piston can be freed.
TROUBLESHOOTING MECHANICAL FAILURES ON A
REVERSING VALVE BY TEMPERATURE
When operating properly the valve contains refrigerant
gases at certain temperatures. The discharge line should be
the same temperature after the valves discharge line.
