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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
Ohm Meter Range
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
C- Heating Components
1. Ignitor
The SureLight
®
ignitor is made of durable silicon nitride. Ig
nitor longevity is enhanced by controlling voltage to the ig
nitor. The integrated control provides a regulated 120 volts
to the ignitor for a consistent ignition and long ignitor life.
Ohm value should be 39 to 70. The ignitor is located on the
bottom of the air gas plenum (figure 13). See figure 14 for
ignitor check out.
NOTE -
The SL297UHNV furnace contains electronic
components that are polarity sensitive. Make sure that the
furnace is wired correctly and is properly grounded.
2. Flame Sensor
A flame sensor is located on the bottom of the air gas
plenum. See Figure 13. The sensor can be removed for
service without removing the the burner. During operation,
flame is sensed by current passed through the flame and
sensing electrode. The SureLight control allows the gas
valve to remain open as long as flame signal is sensed. To
check flame sense signal use the push-button found on the
integrated control and go to Field Test Mode. The menu will
display the flame signal. See Table 15 for flame signal.
TABLE 15
Flame Signal in Microamps
Normal
Low
Drop Out
2.6 or greater
2.5 or less
1.1
