4-24. ELECTRICAL SYSTEM
This task covers
Shop Equipment, Automotive
Maintenance and Repair,
Main Engine Shutdown (see para. 2-10)
APU Shutdown (see para. 2-12)
Battery Switch OFF
110 Volt Inverter OFF
LHS and RHS Engine Cover Removed
(see para. 4-12.11)
If the batteries are undercharged carry out tests 1 thru 11. If the batteries are overcharged, or
showing low electrolyte level, carry out test 12 thru 14.
Be sure undercharging is not a result of accessories being left on. With all accessories off and battery
switch set to BOTH and batteries charged, connect a voltmeter between the terminals of the current shunt.
The reading should be zero even in the millivolt range. If there is a reading, check for a broken accessory
switch or an accessory circuit connected directly to the battery bus bar. The current shunt is mounted on
the left hand engine lifting bracket.
Be sure alternator drive belts are tight. There should be a maximum 1/2 in. (12 mm) play in drive belt at
the mid-position between the pulleys.
Be sure all battery, starter motor, alternator, and ground connections are tight and clean. Be sure battery
posts are not coated with corrosion products.
Switch ignition on and note dash-mounted voltmeter reading. A zero reading indicates wire 22 or 21 or the
wires between the batteries and battery switch are broken. It may also indicate a fault with the battery
switch or the ignition switch. Check all wire and switches and replace failed components.
Change 4 4-412