Thermo King MD-MT - Starter Engagement and Crank Timing Diagnosis

CYCLE-SENTRY Diagnosis
142
Unit cranks only after preheat has
occurred for approximately 6
minutes
Defective engine temperature
thermistor
Test engine temperature thermistor
Open BL1 or BL2 wires from option
board to engine temperature
thermistor
Check BL1 and BL2 wires
Defective CSM Test or replace CSM
Starter cranks 4 to 5 seconds
only and disengages
Defective or improperly adjusted
RPM sensor
Test RPM sensor
Open FS-1 or FS-2 circuit from the
RPM sensor to the option board
Test FS-1 and FS-2 circuits
Starter not cranking engine above
50 RPM
Test starter, battery voltage and
cranking speed
Defective CSM Test or replace CSM
Starter disengages before 4 to 5
seconds and before engine starts
Defective CSM Replace CSM with known good one.
Do not rely on bench test of CSM
Low battery voltage or condition Test battery
Poor connection or excessive
voltage drop from battery positive
post to 7A circuit on the option
board or from CH on the option
board to negative battery post
While starter is engaging, test
voltage drop from battery positive
post to 7A on option board, and test
voltage drop from battery negative
post to CH on option board
Unit does not disengage starter
when engine is started
Defective CSM Test or replace CSM
Defective start relay Test or replace start relay
Unit keeps starter engaged for
approximately 4 seconds even if
engine starts in less than 4
seconds
Defective or improperly adjusted
RPM sensor
Test RPM sensor
Open FS-1 or FS-2 circuit from the
RPM sensor to the option board
Test FS-1 and FS-2 circuits
Defective CSM Test or replace CSM
Condition Possible Cause Test Procedure