TM10-3950-672-24-2
If the lamp goes out, there is a short in the switch.
Switch On, Lamp Off, Engine Stopped
This condition can be caused by an open in the circuit.
To determine where an open exists. Check for a blown
fuse, a burned out bulb, defective bulb socket, or an
ignition switch.
Switch On, Lamp On, Engine Running
Check the drive belt and alternator pulley to be sure the
alternator is rotating.
Disconnect the lead to Terminals No. 1 and No. 2. If
the lamp stays on, there is a short to ground on the
alternator side of the lamp.
5-151