Test Procedures
Controller
The controller’s software operation is confirmed if it
is functioning. Execute the test to confirm its
operation of the loads. Illumination of a diagnostic
code (other than E) is not an indication of controller
failure. Each code requires its own diagnosis.
Harvest assist solenoid
1. Test using the controller’s indicator lights. Push
and release the Harvest button. The Hot Gas
indicator light will be on. At the same time the
Harvest Assist Solenoid will be powered. If the ice
on the evaporator is thin, the solenoid will extend. If
the ice is nearly full sized, the solenoid will press
against the ice until it releases from the evaporator,
then the solenoid probe will extend. If the probe
extends, the solenoid is good. If not, do a voltage
check. Unplug the high voltage harness from the
harvest assist solenoid. Attach a voltmeter to the
harness connector. Push and release the Harvest
button. There should be full voltage at the
connector. If there is and the solenoid does not
extend, replace the solenoid. If full voltage is not
present, check voltage at the controller. If there is
no voltage, check voltage from the controller to
ground. The hot gas / harvest assist pin is 5. If
there is voltage from that pin to ground, but low
voltage at the solenoid harness connection, the
harness has a broken wire or poor connection and
must be replaced. If the voltage to ground is low,
the controller should be replaced.
Note: The coil of this valve is internally rectified, will
normally show infinite resistance when tested with
an ohmmeter.
Hot Gas Valve
1. Test using the controller’s indicator lights. If the
unit is running, or has been off for more than 4
minutes, push and release the Harvest button. The
Hot Gas indicator light will be on and the hot gas
valve will be energized. The compressor will force
discharge gas into the evaporator inlet, warming it.
If the evaporator inlet does not warm up, do a
voltage check. Shut the unit off by holding the Off
button in for 3 seconds. Unplug the high voltage
harness from the hot gas solenoid. Attach a
voltmeter to the harness connector. Wait 4
minutes. Push and release the Harvest button.
There should be full voltage at the connector. If
there is and the solenoid does not open, replace
the solenoid coil. If full voltage is not present, check
voltage at the controller. If there is no voltage,
check voltage from the controller to ground. The
hot gas pin is 5. If there is voltage from that pin to
ground, but low voltage at the solenoid harness
connection, the harness has a broken wire or poor
connection and must be replaced. If the voltage to
ground is low, the controller should be replaced.
2. Test with an ohmmeter.
Disconnect electrical power.
Unplug high voltage harness from hot gas or vapor
valve. Measure resistance of hot gas or vapor
valve coil. If open, replace the coil.
May 2008
Page 40
CU1526, CU2026, CU3030
Service Manual
Electrical Shock
Hazard
.
Disconnect electrical
power before
beginning removal
procedure.