Triumph Thunderbird Service Manual page 28

Starting Circuit
All Triumph models are equipped with an electric start
system. This system consists of a starter relay, starter
motor, starter switch, sidestand switch, engine stop switch,
clutch switch and the sprag clutch. The starter motor is
connected to the starter relay and the battery by heavy
duty cables in order to supply the large currents required
by the motor to start the engine. When the starter button
is pressed the relay is energised, which then allows current
to the starter motor. The starter motor will not operate
unless the clutch lever is pulled in. Also, the starter will not
operate if the sidestand is down, unless the transmission is
in neutral. If the starter motor does not operate, the
following basic checks must be carried out before further
diagnosis is performed:
Check the engine stop switch is in the 'RUN'
position.
Check the battery terminals are clean and tight.
Check the frame and engine earth connections
are clean, tight and free from corrosion.
Ensure the battery is fully charged and in good
condition.
Check that any fuse in the circuit is not blown
and is of the correct rating.
Using the Triumph Diagnostic Tool, check the
operation of the neutral switch or gear position
sensor (if fitted), sidestand and clutch switches.
Note:
• On all new models from Daytona 675 onwards,
which use a CAN connection between the
instruments and the ECM, the engine will not
crank if the instruments are disconnected.
Rectify any defects as necessary.
Symptom
Possible cause(s)
Starter relay does not click, starter motor does not turn Battery discharged or defective
Blown main or starter relay fuse
Defective starter relay wiring or starter switch
Check that the sidestand, transmission and clutch lever are
positioned for engine starting I.E. transmission in neutral,
clutch lever pulled in and the sidestand down
Defective alarm system - ensure any alarm fitted is working
correctly
Starter motor turns slowly Battery discharged or defective
Loose, corroded or dirty battery connections
Loose, corroded or dirty starter motor or starter relay
connections
Defective starter motor
Loose, corroded or dirty battery ground connections
Starter relay clicks but engine does turn over Battery discharged or defective
Crankshaft does not turn due to engine defect
Defective starter motor
Starter cable open circuit
Defective starter relay
Starter motor turns but engine does not turn over Starter motor or starter ring gear
1.20
SelVice Manual - Thunderbird