Service Manual

10.21
ELECTRICAL
10
CHARGING SYSTEM
Current Draw - Key Off
Connect an ammeter in series with the negative battery cable.
Check for current draw with the key off. If the draw is excessive,
loads should be disconnected from the system one by one until
the draw is eliminated. Check component wiring as well as the
component for partial shorts to ground to eliminate the draw.
Charging System “Break Even” Test
The “break even” point of the charging system is the point at
which the alternator overcomes all system loads (lights, etc.)
and begins to charge the battery. Depending on battery condition
and system load, the break even point may vary slightly. The
battery should be fully charged before performing this test.
1. Connect a tachometer to the engine.
2. Using an inductive amperage metering device, (set to DC
amps) connect to the negative battery cable.
3. With engine off and the key, kill switch, and lights in the
ON position, the ammeter should read negative amps
(battery discharge). Reverse meter lead if a positive reading
is indicated.
4. Shift transmission into neutral with the park brake on and
start the engine. With the engine running at idle, observe
meter readings.
5. Increase engine RPM while observing ammeter and
tachometer.
6. Note RPM at which the battery starts to charge (ammeter
indication is positive).
7. With lights and other electrical loads off, the “break even”
point should occur at approximately 1500 RPM or lower.
8. With the engine running, turn the lights on and engage
parking brake lock to keep brake light on.
9. Repeat test, observing ammeter and tachometer. With
lights on, charging should occur at or below 2000 RPM.
Alternator Output
RPM AMPS VOLTS
2500 20 13.2 Vdc
CAUTION
Do not connect or disconnect the battery cable
or ammeter with the engine running. Damage will
occur to electrical components.
Current Draw - Key Off:
Maximum of .01 DCA (10 mA)
Current Draw Inspection
Key Off
30 Amp
CAUTION
Do not allow the battery cables to become
disconnected with the engine running. Follow the
steps below as outlined to reduce the chance of
damage to electrical components.
WARNING
Never start the engine with an ammeter
connected in series. Damage to the meter or
meter fuse will result.
Do not run test for extended period of time.
Do not run test with high amperage accessories.