Test batteries for
weak cells.
Replace alternator.
Connect voltmeter between alternator 12-volt terminal and ground terminal.
Take reading with cab power ON and engine running.
POSSIBLE CAUSES
Belt loose or broken. No input to alternator terminals. Damaged alternator.
Corroded or loose battery connection. Battery discharged.
PROBLEM 4
Engine runs, but battery is not charging.
CHECKS
Check drive belt for correct tension.
(See engine manual for drive belt deflection specifications.)
OK
Not OK
Zero Volts DC
13.6 Volts DC or Less
13.6 Volts DC or More
Tighten drive belt
or replace belt.
Repair wiring or
connections.