Group 30: Electrical system Repair instructions
27
Checking the charging system
Special tools: 9812519
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 out-
put depends on the alternator revolution. When the en-
gine is started an excitation current is needed to
“wake up” the alternator.
NOTE! It is the consumers (batteries included) which
decides the output current from the alternator.
Measurements
1. Engine off.
2. Use multimeter 9812519 to do a voltage measure-
ment over the battery. The nominal voltage over a
full loaded battery is approx. 25.4V.
3. Engine on. Run at 1500 rpm.
4. Use multimeter 9812519 to do a voltage measure-
ment over the battery. The nominal charging volt-
age over the battery should be approx. 27.8-
28.6V.
Fault tracing charging system
Battery
1. Check that all connectors at the battery is correct
assembled.
2. Check the conditions of the cables to the battery.
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 is correct assembled.
3. Check the conditions of all cables in the charging
system.
4. Regulator fault, try another alternator.
when undercharge
1. Check the alternator belt tension.
2. Check that all connectors at the alternator and at
the battery is correct assembled.
3. Check the conditions of all cables in the charging
system.
4. Regulator fault, try another alternator.
when overcharge
1. Probably regulator fault, try another alternator.
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