Service Manual
58
TROUBLESHOOTING
Troubleshooting circuit board FAST #
1185237, 1186140
The Communicating Series outdoor units all use the same
control board. A model plug is used to identify the system
type, and set the operating parameters for airflow, start
circuit timing etc. (See Model Plug section.)
Replacement boards may have a different part number from
the original board. A newer board will always be backward
compatible to previous units if it is superseded at Fast Parts.
Old boards are not always forward compatible due to new
functions, or software changes made to resolve field issues.
Systems Communication Failure
If communication with the Communicating control is lost with
the wall control, the control will flash the appropriate fault
code. (See Table 17.) Check the wiring to the wall control
and the indoor and outdoor units.
Pressure Switch Protection
The outdoor unit is equipped with high- and low- pressure
switches. If the control senses the opening of a high- or
low- pressure switch, it will respond as follows:
1. De- energize the appropriate compressor contactor.
2. Keep the outdoor fan operating for 15 minutes.
3. Display the appropriate fault code (see Table 17).
4. After a 15 minute delay, if there is a call for cooling or
heating and LPS or HPS is reset, the appropriate
compressor contactor is energized.
5. If LPS or HPS has not closed after a 15 minute delay,
the outdoor fan is turned off. If the open switch closes
anytime after the 15 minute delay, then resume
operation with a call for cooling or heating.
6. If LPS or HPS trips 3 consecutive cycles, the unit
operation is locked out for 4 hours.
7. In the event of a high- pressure switch trip or high-
pressure lockout, check the refrigerant charge,
outdoor fan operation, and outdoor coil (in cooling) for
airflow restrictions, or indoor airflow in heating.
8. In the event of a low- pressure switch trip or low-
pressure lockout, check the refrigerant charge and
indoor airflow (cooling) and outdoor fan operation and
outdoor coil in heating.
Control Fault
If the outdoor unit control board has failed, the control will
flash the appropriate fault code (see Table 17). The control
board should be replaced.
Brown- Out Protection
If the line voltage is less than 187v for at least 4 seconds,
the appropriate compressor contactor and fan relay are
de- energized. Compressor and fan operation are not
allowed until voltage is a minimum of 190v. The control will
flash the appropriate fault code (see Table 17).
230v Brown- Out Protection Defeated
The brownout feature can be defeated if needed for severe
noisy power conditions. This defeat should always be a last
resort to solving the problem. Defeat is available for
Communicating systems on the wall control or outside
board, or it can be initiated through the forced defrost pins
for non- communicating systems as follows:
The brownout toggle is accomplished by shorting the defrost
pins from power up with the OAT and OCT sensor
connector removed. After 3 seconds, the status of the force
defrost short and the OAT/OCT as open will be checked. If
correct, then the brownout will be toggled.
S Status code 6 shows the brownout is disabled.
S Status code 5 shows the brownout is active.
After the brownout defeat is set, power down and reinstall
the OAT/OCT sensor and remove the short from the forced
defrost pins. As long as the short on the forced defrost
remains, the OAT and OCT faults will not be cleared. The
code will continue to be flashed.
The control is shipped with the brownout active. The change
in status is remembered until toggled to a new status. A
power down/power up sequence will not reset the status. It
may be necessary to do the toggle twice to cycle to the
desired state of the defeat.
230V Line (Power Disconnect) Detection
If there is no 230v at the compressor contactor(s) when the
indoor unit is powered and cooling or heating demand
exists, the appropriate fault code is displayed. Verify the
disconnect is closed and 230v wiring is connected to the
unit.
Compressor Voltage Sensing
The control board input terminals labeled VS, and L2 on
*CA7, *CA9, *CH6, and *CH9 models (see Fig. 42) are used
to detect compressor voltage status and alert the user of
potential problems. The control continuously monitors the
high voltage on the run capacitor of the compressor motor.
Voltage should be present any time the compressor
contactor is energized and voltage should not be present
when the contactor is de- energized.
Contactor Shorted Detection
If there is compressor voltage sensed when there is no
demand for compressor operation, the contactor may be
stuck closed or there may be a wiring error. The control will
flash the appropriate fault code.
Compressor Thermal Cutout - *CA7, *CA9,
*CH6, *CH9
If the control senses the compressor voltage after start- up
and is then absent for 10 consecutive seconds while cooling
or heating demand exists, the thermal protector is open. The
control de- energizes the compressor contactor for 15
minutes, but continues to operate the outdoor fan. The
control Status LED will flash the appropriate code shown in
Table 17. After 15 minutes, with a call for low or high stage
cooling or heating, the compressor contactor is energized. If
the thermal protector has not re- set, the outdoor fan is
turned off. If the call for cooling or heating continues, the
control will energize the compressor contactor every 15
minutes. If the thermal protector closes, (at the next 15
minute interval check) the unit will resume operation.
If the thermal cutout trips for three consecutive cycles, then
unit operation is locked out for 4 hours and the appropriate
fault code is displayed.
Low or High Contactor Open / No 230V at
Compressor Contactor - *CA7, *CA9, *CH6,
*CH9
If the compressor voltage is not sensed when the
compressor should be starting, the appropriate contactor
may be stuck open or there is a wiring error. The control will
flash the appropriate fault code. Check the contactor and
control box wiring.