Thermo King KD-II SR, Manual

Page: 62 / 182

Electrical Maintenance (Rev. 04/03)
48
The flywheel (rpm) sensor may be checked as follows:
1. Install the flywheel (rpm) sensor into the flywheel;
bracket of the start-stop unit until it contacts the ring
gear. Back out the sensor 1/2 turn and tighten the lock-
nut.
Flywheel (rpm) Sensor
2. Disconnect wires RPM+ and RPM- from the sensor.
3. Place the unit in CONTINUOUS RUN. Run the unit on
low speed and high speed. Check the ac voltage output
across the sensor terminals. Use a meter with a high
ohms per volt internal resistance. A Simpson 260,
Fluke digital or any good VOM will work. However, an
automotive type meter may not give an accurate read-
ing because the meter may load the circuit heavily and
cause the voltage level to appear lower than it actually
is.
a. The output voltage should be 1.0 to 2.0 Vac on low
speed.
b. The output voltage should be 2.0 to 2.5 Vac on
high speed.
NOTE: If the voltage is slightly off, the voltage may be
increased by turning the sensor in more, and the volt-
age may be lowered by turning the sensor out more.
4. Reconnect RPM+ and RPM- wires on rpm sensor.
If the rpm sensor passes the above test, the sensor may be
considered good.
If the unit is not available, an alternate less reliable test may
be performed as follows:
Disconnect the sensor from all wires, and measure the resis-
tance across the terminals and from each terminal to the alu-
minum case. The resistance should be 250 to 300 ohms
across the terminals, and there should be no continuity from
each terminal to the case.
GLOW PLUGS
Glow plugs heat the combustion chamber to aid in quick
starting. The glow plugs are energized when the Preheat-
Start switch is pressed to the PREHEAT or START position
or the microprocessor initiates unit start-up. A defective
glow plug (burned out) can be detected by placing an exter-
nal ammeter in series with the plugs. Normal current draw is
approximately 21 to 25 amps when preheating. A current
draw of 21 to 25 amps means all three glow plugs are work-
ing. If the current draw is less than 21 amps on PREHEAT,
at least one glow plug is bad.
To isolate an open circuit glow plug, remove the jumper bar
and test each glow plug individually with an ohmmeter or a
jumper wire and ammeter. Each glow plug should have a
resistance of approximately 1.5 ohms or a current draw of
about 8 amps.