Lennox CBX25UHV Series Installation And Service Procedure page 12

Test 2: Determine if Unit has Power and
Command Signal
1. Remove the 16­pin low­voltage plug from the motor.
2. With 240V power applied to the air handler, check for
the presences of 24VAC at pins 1 and 12
Figure 7. 16-Pin Power Plug (Pins 1 and 12)
3. Install field-provided test jumper between the plug pins
12 and 15 to apply 24VAC to the motor. Motor should
run at continuous speed. This test isolates the motor
and module from the integrated control. If the motor
runs in this test, motor is good.
Figure 8. 16-Pin Plug (Pins 12 and 15)
Test 2: Determine if Unit has Power and
Command Signal (using TECHMatePro™
service tool)
An option for Test 2 is to use the TECMatePRO
tool (Lennox catalog number X2655) with the 16-pin plug in
to apply 24V to the pins.
Using this tool eliminates the risk of applying power to the
wrong pins.
Since there is very little blower compartment space
removing the plug from the motor and the service tool plug
is easier than trying to use jumpers to place 24VAC to the
correct pins directly on the motor. Follow the instructions
provided with the kit. If the motor runs, do not replace it.
JUMPER
™
service
Figure 9. Using TECHMatPro
Test 3: Testing Motor Windings (Line to Ground)
Ohm out the motor windings from each terminal in the
connector to ground.
● Set the meter to the highest ohms scale.
● If all of these readings are above 100,000 ohms. The
motor is good.
● Typically a good motor will show all readings in infinity
(I), (OL), or (Open). If any of these readings is below
100,000 ohms, the motor has failed and must be
replaced.
Figure 10. Testing Motor Windings (Line to Ground)
Test 3: Testing Motor Windings (Winding to
Winding)
To test the motor through the 3­pin connector;
Winding­To­Winding:
1. Ohm out the phases from one terminal to the other in
the connector.
Page 12
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Tool