16
SYSTEM DIAGNOSIS & TROUBLESHOOTING
The following is a summary of normal and abnormal operation
for typical startup to check out the system. Reference is made
to INSTALLER SETTINGS and SERVICE INFORMATION
screens described above. Refer to training literature for more
details.
Diagnostic information for the heat pump can be obtained
from all of the following sources:
• Controller displays. Refer to training materials for
interpretation of fault messages which appear on the Main,
Fault Status, and Service Needed screens.
• Refrigerant system pressure and temperature measurements
(using standard fi eld service instrumentation)
• LED indicator lights on each of the system’s circuit boards
(see below).
Controller
Normal - As soon as 24 vac power is applied, the blue backlight
of the controller should light up. The “iQ” splash screen will
display the software version. If the System Confi guration
procedure has not been performed yet for this system-controller
combination, “CONFIGURATION NEEDED” will be displayed
across the top (alternating with other information).
If the system has a Type “P” blower motor (shown on SYSTEM
CONFIGURATION and INDOOR FAN STATUS screens), used
in air handlers or G6 gas furnaces, the blower will self-calibrate
for 60 seconds as soon as System Confi guration is completed.
All communications links in COMMUNICATION DATA
should show “OK”. All information displayed in the System
Confi guration screen should be accurate.
Abnormal – If the display is not lit, check that 24 vac is being
provided between the “R” and “C” terminals in the thermostat’s
back connection plate. If not, trace the connection of all
controller wires back to the indoor unit (furnace or air handler).
Check that connections are in accordance with fi eld wiring
diagrams and instructions.
If a SERVICE NEEDED screen with a red backlight is displayed,
a fault has been detected. A brief description of the fault
is displayed on the screen. Access to the FAULT STATUS
screen is permitted.
If communication with the outdoor unit is OK but the unit
size (in tons) shown on the System Confi guration screen in
wrong, contact the service representative of the equipment
distributor. The inverter may not have undergone its initialization
procedure, performed at the factory.
Outdoor Unit Inverter
WARNING
ELECTRIC SHOCK HAZARD!
Disconnect power before servicing the
outdoor unit. Failure to follow these
instructions may result in electric shock or
death. Trouble-shooting the outdoor unit
may require that power be restored with
the control panel cover removed. Become
familiar with the control panel and hazardous
voltage areas before proceeding.
Time is required for inverter voltage to bleed
down after removal of line power. Wait at least
60 seconds after removing line voltage before
touching any inverter parts or wiring.
Normal – Examine the following with the control panel cover
off. Note the two smaller circuit boards mounted on a metal
“bridge” over the inverter. The red LED behind the upper right
side of the bridge should be lit and on steady when power is
applied to the inverter. Refer to Figures 3 and 12.
Abnormal –The red LED behind the upper right side of the
bridge is not lit. In this case, power is not being provided to
the inverter. Check that line voltage is being applied to the
bottom of the contactor. If so, check that 24 vac is being
provided across the contactor coil. If not, check the control
power wiring (RED and GRY wires) for 24 vac. Check that
the high pressure switch is closed. A fault indicating OD
UNIT COMM FAULT or OD UNIT LOST POWER would also
result from no line voltage applied.
The red LED behind the upper right side of the bridge is lit
but blinking. This indicates that the inverter is powered up
and that it detects a fault condition. If the controller does not
display a fault message, put the unit into HEAT or COOL
mode, and a message will be displayed. NOTE: When
line power is removed, the red LED will blink for about 1
minute before going out. Check that the 3- and 4-position
communication plugs are connected to the terminals marked
“INVERTER” and “INDOOR” on the right side of the outdoor
interface board.
Outdoor Unit Interface Board (right side small
circuit board)
Normal – Refer to Figure 13. The red LED at the upper left
of this board should do a “heartbeat” blink, consisting of a
double-blink followed by a pause, repeated. Note 4 other
LEDS towards the lower edge of the board. When the
compressor is off, the 3rd LED from the right should be
on (crankcase heater). When the compressor is running
in heating, the 2nd LED from the right should be on (EXV
enabled to open). When the unit is heating and in a defrost
cycle, the 1st and 4th LEDs from the right should be on.