Lennox SL280UHNV Series

Page 26
Troubleshooting Motor Windings
Ensure that motor windings are not damaged by perform
ing the following tests:
NOTE - If your ohm meter is not an auto-ranging type, set it
to the highest ohm scale (100k ohms or greater) before
performing tests.
TABLE 14
Scale
Measurement Range
in words ohms
2M
two megohm -- two
million ohms
0-2,000,000
200k
two hundred kilohm
-- two hundred thou
sand ohms
0-200,000
20k
twenty kilohm --
twenty thousand
ohms
0-20,000
2k
two kilohm -- two
thousand ohms
0-2,000
200 two hundred ohm 0-200
FIGURE 10
TEST A
Measure the resistance between each of the three motor
leads (3-pin plug) and the unpainted part of the end shield.
If the winding resistance to ground is <100k
ohms, replace the motor and control module. If
the resistance to ground is >100k, the motor
windings are fine. Proceed to Test B.
Test A
FIGURE 11
TEST B
Use an ohmmeter to measure the motor phase-to-phase
resistance by checking these combinations of the the 3-pin
motor plug. For the purpose of this test, start at either end of
the connector as lead 1.
1 - The lead-to-lead resistance across any two leads
should be less than 20 ohms.
2 - Each lead-to-lead resistance should be the same.
If the measured resistance is greater than 20 ohms, re
place the motor and control module.
Test B
FIGURE 12