15
Troubleshoot the Defrost System
The defrost control is equipped with a set of pins (labeled TEST
on control circuit board) to aid in troubleshooting the defrost
system. Connecting the test pins speeds up the defrost cycle
time by a factor of 256.
1. Disconnect power.
2. Remove control box cover.
3. Connect the test pins on the defrost control using a test
jumper wire.
NOTE: If the outdoor temperature is above 32°F (0ºC),
connect the defrost sensor terminals using a test jumper wire.
See “Defrost Control Board” in “Adjust Defrost System.”
4. Replace control box cover.
5. Reconnect power.
6. Start system in heating operation.
7. Time the defrost test cycle as determined by the chart. After
the corresponding defrost cycle time from the chart below
has elapsed, the reversing valve should shift to defrost mode
and the outdoor fan should stop. After 2 seconds of defrost
operation, the reversing valve should shift back to heating
operation and the outdoor fan should start.
NOTE: If this procedure is not observed, check the reversing
valve solenoid for correct operation by measuring
temperatures and pressures under heating and cooling
modes. If the reversing valve solenoid operates correctly then
replace the defrost control board. See “Sequence of
Operation.”
8. If an adjustment is required, see “Adjust Time Between
Defrost Cycles” in “Adjust Defrost System.”
9. Disconnect power.
10. Remove control box cover.
11. Remove jumper from test pins and jumper from defrost
sensor terminals, if used.
12. Replace control box cover.
13. Reconnect power.
TROUBLESHOOTING
Heat Pump Fails to Operate Properly
Review “Sequence of Operation” and visually inspect the heat
pump before troubleshooting:
System Diagnostic Module
W4GH8 heat pumps contain a diagnostic module for
troubleshooting heat pump system failures. By monitoring and
analyzing data from the compressor and thermostat demand, the
module can accurately detect the cause of electrical and system
related failure without any sensors. If a system problem occurs, a
flashing LED indicator communicates the failure code.
LED Description
Power LED (Green) indicates voltage is present at the power
connection of the module.
Alert LED (Yellow) communicates an abnormal system condition
through a unique flash code. The Alert LED will flash a number of
times consecutively, pause, and then repeat the process. The
number of consecutive flashes correlates to a particular
abnormal condition.
Trip LED (Red) indicates there is a demand signal from the
thermostat but no current to the compressor is detected by the
module. The Trip LED typically indicates the compressor
protector is open or may indicate missing supply power to the
compressor.
Diagnostic LEDs Interpretation
When an abnormal system condition occurs, the diagnostic
module displays the appropriate Alert and/or Trip LED. The
yellow Alert LED will flash a number of times consecutively,
pause, and then repeat the process. To identify a flash code
number, count the number of consecutive flashes. Refer to the
Flash Codes chart for information on the flash codes.
Every time the module powers up, the last Alert LED flash code
that occurred prior to shutdown is displayed for 60 seconds. The
module will continue to display the previous flash code until the
condition returns to normal or 24 VAC is removed from the
module. Trip and Alert LEDs flashing at the same time means
control circuit voltage is too low for operation.
WARNING
Electrical Shock Hazard
Disconnect power before servicing.
Replace all parts and panels before operating.
Failure to do so can result in death or electrical shock.
Defrost Control Setting
Defrost Test Cycle Time
T1 - 30 minutes
7 seconds
T2 - 60 minutes
14 seconds
T3 - 90 minutes
21 seconds
WARNING
Electrical Shock Hazard
Disconnect power before servicing.
Replace all parts and panels before operating.
Failure to do so can result in death or electrical shock.
