Checking the charging system
Tools:
88890074 Multimeter
Generally about alternators:
The voltage output from an alternator must be limited
to prevent the elecrolyte in the battery to evaporate.
The alternator output is regulated (limited) by the volt-
age regulator in the alternator. The maximum current
that the alternator can deliver at regulated voltage
output depends on the alternator revolution. When the
engine is started an excitation current is needed to
“wake up” the alternator.
NOTICE! It is the consumers (batteries included)
which decides the output current from the alternator.
Fault tracing charging system
Battery check
1 Check
that
all connectors at the battery are cor-
rectly assembled.
2 Check the condition of the cables to the bat-
tery.Look for oxidation.
3 Check the water level in the battery.
4 Check, if possible, the specific gravity of all cells.
when no charge
1 Check the alternator belt tension.
2 Check that all connectors at the alternator and
at the battery are correctly assembled.
3 Check the condition of all cables in the charging
system.
4 Regulator fault. Replace regulator.
when undercharge
1 Check the alternator belt tension.
2 Check that all connectors at the alternator and
at the battery are correctly assembled.
3 Check the condition of all cables in the charging
system.
4 Regulator fault. Replace regulator.
when overcharge
1 Probably regulator fault. Replace regulator.
Measurements
1 Engine off.
2 Use 88890074 Multimeter to do a voltage meas-
urement over the battery. The nominal voltage
over a full loaded battery is approx. 25.4 V.
3 Engine on. Run at 1500 rpm.
4 Use 88890074 Multimeter to do a voltage meas-
urement over the battery and also over the alter-
nator. The nominal charging voltage over the
battery should be approx. 27.8-28.6 V.
30-0 General
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