SERVICING
31
Electrical Checks - High Voltage Power Circuits
WARNING
High Voltage!
Disconnect all power before servicing
or installing this unit. Multiple power
sources may be present. Failure to do
so may cause property damage, personal
injury or death.
1. Disconnect power to the furnace.
2. Disconnect the 5-circuit power connector to the ECM
motor.
3. Turn on power to the furnace.
WARNING
Line voltage now present
4. Measure voltage between pins 4 and 5 on the 5-circuit
connector. Measured voltage should be the same as
the supply voltage to the furnace.
5
4
3
2
1
Lines 1 and 2 will be connected
for 120VAC Power Connector
applications only
Gnd
AC Line Neutral Connection
AC Line Hot Connection
}
Power Connector
(1/2 HP Motors)
“Motor Half”
(Viewed from Plug End)
5
4
3
2
1
Lines 1 and 2 will be connected
for 120VAC Power Connector
applications only
Gnd
AC Line Neutral Connection
AC Line Hot Connection
}
inductor
Power Connector
(3/4 & 1 HP Motors)
“Motor Half”
(Viewed from Plug End)
5. Measure voltage between pins 4 and 3. Voltage should
be approximately zero.
6. Measure voltage between pins 5 and 3. Voltage should
be the same as the supply voltage to the furnace.
7. If no voltage is present, check supply voltage to the
furnace.
8. Disconnect power to the furnace. Reconnect the
5-circuit power harness disconnected in step 2.
Electrical Checks - Low Voltage Control Circuits
1. Turn on power to the furnace.
WARNING
Line voltage now present
2. Check voltage between pins 1 and 4 on the 4-wire motor
control harness between the motor and control board.
Voltage should be between 3 and 15 VDC.
3. If no voltage is present, check control board.
Motor Control/End Bell Checks
WARNING
High Voltage!
Disconnect all power before servicing
or installing this unit. Multiple power
sources may be present. Failure to do
so may cause property damage, personal
injury or death.
1. Disconnect power to the furnace.
NOTE: Motor contains capacitors that can hold a
charge for several minutes after disconnecting
power. Wait 5 minutes after removing power to
allow capacitors to discharge.
2. Disconnect the motor control harness and motor power
harness.
