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SERVICING
High Voltage
Connections
C L G N
1 2 3 4 5
Low Voltage Connections
EEM Motor Connections
Checking ECM Motors
An ECM is an Electronically Commutated Motor which
offers many significant advantages over PSC motors.
The ECM has near zero rotor loss, synchronous machine
operation, variable speed, low noise, and programmable
air flow. Because of the sophisticated electronics within
the ECM motor, some technicians are intimated by the
ECM motor; however, these fears are unfounded. GE/
Regal Beloit offers two ECM motor testers, and with a VOM
meter, one can easily perform basic troubleshooting on
ECM motors. An ECM motor requires power (line voltage)
and a signal (24 volts) to operate. The ECM motor stator
contains permanent magnet. As a result, the shaft feels
"rough" when turned by hand. This is a characteristic of
the motor, not an indication of defective bearings.
Line voltage now present
1. Disconnect the 5-pin connector from the motor.
2. Using a volt meter, check for line voltage at terminals
#4 & #5 at the power connector. If no voltage is
present:
3. Check the unit for incoming power.
4. Check the control board.
16
3/16"
1/4"
WARNING
5. If line voltage is present, reinsert the 5-pin connector
and remove the 16-pin connector.
6. Check for signal (24 volts) at the transformer.
7. Check for signal (24 volts) from the thermostat to the
"G" terminal at the 16-pin connector.
8. Using an ohmmeter, check for continuity from the #1
& #3 (common pins) to the transformer neutral or "C"
thermostat terminal. If you do not have continuity,
the motor may function erratically. Trace the common
circuits, locate and repair the open neutral.
9. Set the thermostat to "Fan-On". Using a voltmeter,
check for 24 volts between pin # 15 (G) and common.
10. Disconnect power to compressor. Set thermostat to
call for cooling. Using a voltmeter, check for 24 volts
at pin # 6 and or #14.
11. Set the thermostat to a call for heating. Using a
voltmeter, check for 24 volts at pin #2 and/or #11.
}
1
Lines 1 and 2 will be connected
for 12OVAC Power Connector
2
applications only
3
Gnd
4
AC Line Connection
5
AC Line Connection
OUT -
8
ADJUST +/-
7
Y1
6
COOL
5
DELAY
4
3
COMMON2
2
W/W1
COMMON1
1
16-PIN ECM HARNESS CONNECTOR
If you do not read voltage and continuity as described, the
problem is in the control or interface board, but not the
motor. If you register voltage as described , the ECM power
head is defective and must be replaced.
OUT +
16
15
G (FAN)
14
Y/Y2
13
EM Ht/W2
24 Vac (R)
12
HEAT
11
10
BK/PWM (SPEED)
O (REV VALVE)
9
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