Trane ACONT900AC43UA Service Manual page 76

Outdoor Fan Motor
Introduction
Communicating outdoor unit models feature ECM type
outdoor fan motors. The motors are powered by 240
volt line voltage and are speed controlled via a PWM
voltage signal from the outdoor unit control board.
Troubleshooting
If the outdoor fan motor fails to run, or fails to run at
the proper speed, the problem will be either a failed
motor, lack of line voltage to the motor, or a failed
outdoor unit control board.
Step 1
Verify a call for cooling is present by checking the Y1
and Y2 LED light on the outdoor unit control board.
Figure 1
Step 2
Check for 240 volt line voltage to the motor between
terminals 6 and 3 of the 6 pin motor connection plug.
Perform this check on the motor side of the plug (Figure
2). If voltage is not present, Verify the plug connection
is properly seated and/or correct the line voltage
problem to the motor. If line voltage is present, continue
to the next step.
Figure 2
HP - F 2
Step 3
With line voltage verified, check for the motor speed
command from the control board. Set digital
multimeter to read DC voltage. Check for DC voltage
between TEST COMMON and the PWM pin on plug
J3 of the outdoor unit control board (Figure 3). DC
voltage should be present during a call for Y1 or Y2
Cooling/Heating operation.
Figure 3
Proper DC voltage ranges between TEST COMMON
and the PWM pin on plug J3 are:
Y1 call: 5-7 VDC
Y2 call: 7.5-10 VDC
Defrost soft switch-over: 0.5 VDC
Step 4
If proper DC voltage is present, along with proper line
voltage, yet the motor does not run, replace the motor.
If line voltage is present, but proper voltage is not
present between the PWM pin on J3 and TEST
COMMON, replace the outdoor unit control board.