Lennox SL280UHNX Series Unit Information page 41

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 13
Ohm Meter Range
Measurement Range
Scale
in words
two megohm -- two million
2M
ohms
two hundred kilohm -- two
200K
hundred thousand ohms
twenty kilohm -- twenty
20K
thousand ohms
two kilohm -- two thousand
2K
ohms
200 two hundred ohm
FIGURE 12
Measure the resistance between each of the three motor
leads (3-pin plug) and the unpainted part of the end shield.
ohms
0-2,000,000
0-200,000
0-20,000
0-2,000
0-200
Use an ohmmeter to measure the motor phase-to-phase
resistance by checking these combinations of 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
2 - Each lead-to-lead resistance should be the same. If
Page 41
TEST A
If the winding resistance to ground is <100k ohms,
replace the motor and control module. If the resis-
tance to ground is >100k, the motor windings are
fine. Proceed to Test B.
Test A
FIGURE 13
TEST B
should be less than 20 ohms.
the measured resistance is greater than 20 ohms,
replace the motor and control module.
Test B
FIGURE 14