Carrier 50FC 08-16 Series Service And Maintenance Instructions page 8

TROUBLESHOOTING THE ECM MOTOR
EcoBlue™ motors are designed with several built-in protections
included in the motor software. If the motor detects a fault it will
safely shut down. See Table 5, "Supply Fan Motor Logic and
Safety Relays" on page 34 for a complete list.
Troubleshooting the motor requires a voltmeter.
1. Disconnect main power to the unit.
2. Disconnect motor plug in supply section of the unit.
3. Restore main unit power.
4. Check for proper line voltage at motor power leads Black
(PL1-1), Yellow (PL1-2), and Blue (PL1-3). Blue is only
present on 3-phase motors. See the following table.
50FC UNIT
MOTOR VOLTAGE
VOLTAGE
208/230
460
575
5. Disconnect main power.
6. Reconnect motor plug in supply section of unit.
7. Restore main power.
8. Check for proper motor control voltage signal of 9.7 vdc
to 10.3 vdc at IFM-1 and IFM-3 on Unit Control Board
(UCB). See Fig. 12.
9. Using a jumper wire from unit control terminals R to G,
engage motor operation.
10. Verify control signal from user speed selection switch by
placing voltmeter taps in provided terminals marked vdc.
Signal should be between 3.8 vdc and 10.3 vdc.
11. If the motor does not start and run, remove the fan assem-
bly and replace the motor with one having the same part
number. Do not substitute with an alternate design motor
as the voltage/speed programming will not be the same as
that on an original factory motor.
MIN-MAX VOLTS
230 187-253
460 360-506
575 517-633
Fig. 12 — Supply Fan Control Wiring Diagram
8