Lennox EL297UH045XV36B Unit Information page 51

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
Scale Measurement Range
in words
2M two megohm -- two
million ohms
200K two hundred kilohm --
two hundred thousand
ohms
20K twenty kilohm -- twenty
thousand ohms
2K two kilohm -- two thou-
sand 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.
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.
ohms
0-2,000,000
0-200,000
0-20,000
0-2,000
0-200
TEST A
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,
replace the motor and control module.
Models with the Lennox Blower Drive
Removed the three blower leads from the blower drive.
see TEST A. If ohms to ground shows resistance replace
motor. If the circuit is open move to test B and table below
for acceptable resistance. If ohm reading is met motor has
passed. If the motor passes both test A and B and the
shaft spins freely by hand, replace the blower drive.
Motor HP
1/2
3/4
1
Page 51
Test A
FIGURE 13
TEST B
Test B
FIGURE 14
Ohm Reading
7.6 + .76
6.3 + .63
4.7 + .47