Service Manual

ISB, ISBe and QSB (Common Rail [...] Key Switch
Section 13 - Electrical Equipment - Group 13 Page 13-29
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If the lamp is off when the switch is in the ON position and
the engine is not running, there can be an open circuit.
Check for a blown fuse, a burned out bulb, defective bulb
socket, or an open circuit in number 1 or "D+" lead
between alternator and keyswitch.
If the lamp is on when the switch is on and the engine is
running, disconnect the lead to the alternator.
• If the lamp stays on, there is a short to ground in the
lamp circuit. Refer to Procedure 013-001
• If the lamp goes out, inspect the alternator. Refer to
Procedure 013-001
Key Switch (013-030)
Voltage Check
WARNING
Be sure the key switch is in the OFF position to
reduce the possibility of electrical shock and personal
injury.
Remove the wire connecting the keyswitch to the
magnetic switch (marked S or Start) from the keyswitch
terminal.
Connect the positive (+) lead of digital multimeter, Part
Number 3377163, or equivalent, to the keyswitch terminal
and the negative (-) lead to a chassis or engine ground
location.
NOTE: Set the multimeter to indicate DC volts with the
keyswitch in the OFF position. There must be no voltage
at the keyswitch terminal. If the meter indicates voltage,
the keyswitch is malfunctioning and must be replaced.