Trane Precedent TSCSeries Installation And Maintenance Manual page 58

Troubleshooting
Please follow steps sequentially unless directed differently
in solution.
Table 15. Troubleshooting for direct drive plenum fan
Step Symptom or Test
Obstruction blocking
1 operation of evaporator
fan.
Check line to line voltage
2 at pin 1, 2, and 3 of PPF-
IDFP.
Verify continuity across
3 fuse FU31, FU32, and
FU33.
Measure DC voltage
across pin Vt and com on
4
MMC or note voltage on
ECM display.
Check for 24VAC across
pins A and B on F relay.
5
For units with no F, go to
step 7.
Check for 10VDC across
6 pin 9 on F relay an pin 8
of PPM-IDFC.
Measure DC voltage
across pin Vt and com on
7
MMC or note voltage on
ECM display.
Verify VDC is same
across Vt and com on
8 MMC (or ECM display)
and pin 1 and pin 8 on
PPM-IDFC.
Verify correct wiring
9 connections at KL3 in the
motor.
58
Probable Cause and Solution
If obstruction is present, remove
power from unit and remove
obstruction. Check fan wheel for
damage. Remove wheel/motor
assembly if damaged.
Voltage should be same as line to line
voltage input to unit. If voltage is
same go to step 4. If not, go to step 3.
Replace fuse if continuity is not
present.
Voltage should be greater than 1.0
VDC. If voltage is greater the 1.0, go
to step 8. If not, turn knob on MMC
counter-clock wise 1 turn and check
voltage again. For units with ECM
board increase the output voltage by
3.0 VDC and check voltage again. If
no change in voltage, go to step 5
If voltage is not present, verify
thermostat wiring. Go to step 4. If
voltage is present, go to step 6.
If voltage is not present, check wiring
to F relay. Correct wiring if needed.
Go to step 4. If wiring is correct,
replace relay.
Voltage should be greater than 1.0
VDC. If voltage not present, replace
MMC / ECM board.
If voltage is not same, check for
correct wiring. If voltage is the same
go to step 9.
If wiring is correct, replace motor.
RT-SVX22J-EN