Thermo King 002008, Manual

Page: 49 / 155

Electrical Maintenance
49
Fuse Link
The fuse link is located in the positive battery
cable. The fuse link protects the electric system
from a short in the 2 circuit. If the fuse link burns
out, check for a grounded 2 wire before replacing
the fuse link. Replace the fuse link by replacing
the positive battery cable.
Air Heater
The air heater is mounted on the open end of the
intake manifold. It heats the intake air to help the
engine start in cold weather. The air heater is
energized by the microprocessor during preheat,
just before the engine is started.
The heater is probably defective if the resistance
is more than 0.2 ohms and the current draw is less
than 60 amps, or if the current draw is more than
100 amps.
Check the resistance of the air intake heater with
an ohmmeter between the M6 terminal on the
front of the heater and the screw on the back of
the heater (or the heater case). The resistance
should be 0.1 to 0.2 ohms.
Check the current draw of the heater with a
clamp-on ammeter at the H1 wire near the M6
terminal on the front of the heater. During preheat
the current draw should be approximately
89 amps at 12.5 volts and approximately 77 amps
at 11 volts.
Smart Reefer Multi-Temp µP-IV
Microprocessor Controller
Refer to the appropriate Microprocessor
Controller Diagnosis Manual for complete service
information about the microprocessor controller
and the related components.
Unit Wiring
Inspect the unit wiring and the wire harnesses
during scheduled maintenance inspections for
loose, chaffed or broken wires to protect against
unit malfunctions due to open or short circuits.
AC Components (Model 50
Units Only)
Electrical Contactors
Periodically inspect all contactor points for pitting
or corrosion and repair or replace as necessary.
Test the contact points of the contactor by
checking the voltage drop across each set of
points when the contactor is energized and the
system is operating. If the voltage drop across a
set of points is more than 15 Vac, replace the
contact points as a set.
Test the contactor coil by checking the voltage
across the coil. The contactor coil should be
energized by a minimum of 10 Vdc.
Evaporator Heaters
Test the resistance of each evaporator heater by
disconnecting it from the circuit and checking it
with an ohmmeter. The resistance of each host
evaporator heater should be approximately
122 ohms. The resistance of each remote
evaporator heater should be approximately
106 ohms.
1. M6 Terminal
Figure 20: Air Heater
1
AEA693
CAUTION: Model 50 units use high
voltage ac for electric standby operation.
Lethal voltage potentials can exist on
connections in the high voltage box. Take
appropriate precautions and use extreme
care when testing the unit.