Troubleshooting
RT-SVX23F-EN 51
Troubleshooting Procedures for Direct
Drive Plenum Fan
Prior to troubleshooting, verify all wiring and wiring
connections.The motor has internal protections that will
shut down the motor before damage occurs. A power
cycle is required to reset some of the internal protections.
Before proceeding, power down unit for 1 minute and then
power on.
Please follow steps sequentially unless directed differently
in solution.
Table 13. Troubleshooting for direct drive plenum fan
Step Symptom or Test Probable Cause and Solution
1
Obstruction
blocking operation
of evaporator fan.
If obstruction is present, remove power from
unit and remove obstruction. Check fan wheel
for damage. Remove wheel/motor assembly
if damaged.
2
Check line to line
voltage at pin 1, 2,
and 3 of PPF-IDFP.
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.
3
Verify continuity
across fuse FU31,
FU32, and FU33.
Replace fuse if continuity is not present.
4
Measure DC voltage
across pin Vt and
com on MMC.
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. If no change in
voltage, go to step 5
5
Check for 24VAC
across pins A and B
on F relay.
If voltage is not present, verify thermostat
wiring. Go to step 4. If voltage is present, go
to step 6.
6
Check for 10VDC
across pin 9 on F
relay an pin 8 of
PPM-IDFC.
If voltage is not present, check wiring to F
relay. Correct wiring if needed. Go to step 4.
If wiring is correct, replace relay.
7
Measure DC voltage
across pin Vt and
com on MMC.
Voltage should be greater than 1.0 VDC. If
voltage not present, replace MMC.
8
Verify VDC is same
across Vt and com
on MMC and pin 1
and pin 8 on PPM-
IDFC.
If voltage is not same, check for correct
wiring. If voltage is the same go to step 9.
9
Verify correct wiring
connections at KL3
in the motor.
If wiring is correct, replace motor.
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