10.15
ELECTRICAL
10
Static Thermistor Test
Dynamic Thermistor Test
Hot Lamp Test
Static Thermistor Test
Test Procedure
This test should be conducted with the engine near room temperature. Measure the resistance between
the two yellow/black wires on Pins E and F of SSCB #1 . The thermistor resistance should be 2200-2700
ohms when the engine is at room temperature.
What does passing
this test indicate?
A resistance between 2200-2700 ohms indicates the thermistor is functioning normally and the connection
with the thermistor is in good condition.
What does failing
this test indicate?
If an open or short circuit is found, this test should be repeated between the two yellow/black wires at the
thermistor connector leading directly into the thermistor. An open or short here means there is a problem
inside the thermistor and it must be replaced. If no short or open is found here, the problem is in the yellow/
black wires between the PDM and thermistor.
Dynamic Thermistor Test
Test Procedure
To perform this test, the thermistor will need to be removed from the unit. Place an appropriate container
on a hot plate, add enough water to the container to submerge a thermistor; begin to apply heat. Place the
thermistor and a thermometer in the water. As the water heats, measure the thermistor resistance. To pass
this test, resistance should be 622Ω - 760Ω at 131
o
F (55
o
C), 339Ω - 414Ω at 167
o
F (75
o
C), and 196Ω
- 240Ω at 203
o
F (95
o
C).
What does passing
this test indicate?
Thermistor resistance within specification at each temperature indicates normal operation.
What does failing
this test indicate?
If the thermistor resistance is is significantly out of specification at any of the above temperatures, it should
be replaced.
HOT LAMP Test
Test Procedure
With the ignition switch on and the thermistor and indicator panel unplugged, Check for continuity from
the Blue/white wire at the indicator panel to ground. There should be continuity to ground to pass this test.
What does passing
this test indicate?
The PDM is properly providing a ground path for the HOT LAMP. If the unit passes the test and the HOT
LAMP will not illuminate with the indicator panel and PDM plugged in, and the thermistor unplugged,
inspect the hot lamp bulb and indicator panel, and indicator power source.
What does failing
this test indicate?
If there is no continuity to ground, you may not be testing to a known good ground. There may be damage
to the blue/white wire or connections between the indicator panel and PDM. It is also possible that the
PDM may not be providing a proper ground path. Replace the PDM only after verifying a good ground
path, wiring harness, and connections.
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