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TK 61753-2-MM-EN
A-Series Controller
Refer to the A-Series Trailer Single Temperature Diagnostic Manual TK 61755 for complete service information about
the Controller and related components.
IImmppoorrttaanntt:: A ServiceWatch download can be helpful when diagnosing a problem in a unit with an A-Series Controller.
Therefore, it is recommended that a ServiceWatch download be preformed to help diagnose a problem. A
ServiceWatch download must be preformed before contacting the Thermo King Service Department for
assistance in diagnosing a problem. Refer to the A-Series Trailer Single Temperature Diagnostic Manual TK
61755 for information about downloading the ServiceWatch Data Logger and viewing the data.
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 0.14 ± 0.02 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 70 amps.
Figure 9. Air Heater
1. M6 Terminal
Unit Wiring
Inspect the unit wiring and the wire harnesses during scheduled maintenance inspections for loose, chafed, or broken
wires to protect against unit malfunctions due to open or short circuits.
Wire Harness Routing
Do not change the factory routing of the wire harnesses inside the unit.
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