8.10
Section 8
Electrical System and Components
Troubleshooting Guide - 15/20 amp Battery Charging System
NOTE: Zero ohmmeters and voltmeters on each scale to ensure accurate readings. Voltage tests should be
made with the engine running at 3600 RPM - no load. The battery must be fully charged.
1. If the voltage is 14.7 volts or less, the
charging system is OK; the battery is
unable to hold a charge, or there is a bad
connection between the rectifier-regulator
and battery. Check the wiring harness;
service or replace the battery as
necessary.
If the voltage is more than 14.7 volts, the
rectifier-regulator is faulty. Replace the
rectifier-regulator.
Problem
No
Charge
to
Battery
Test
1. Insert an ammeter in the B+ lead from rectifier-
regulator. With engine running at 3600 RPM and
B+ connected, measure the voltage from B+ (at
terminal on rectifier-regulator) to ground using
a DC voltmeter.
If the voltmeter is 13.8 volts or more, place a
minimum load of 5 amps* on the battery to
reduce the voltage. Observe the ammeter.
*NOTE: Turn on lights (if 60 watts or more) or
place a 2.5 ohm, 100 watt resistor
across the battery terminals.
3a. With the engine stopped, measure the
resistance across stator leads using an
ohmmeter.
3b. With the engine stopped, measure the
resistance from each stator lead to ground
using an ohmmeter.
1. With the engine running at 3600 RPM, measure
the voltage from B+ lead to ground using a DC
voltmeter.
Conclusion
1. If the charge rate increases when load is
applied, the charging system is OK and the
battery was fully charged.
If the charge rate does not increase when
load is applied, test the stator and rectifier-
regulator (tests 2 and 3).
2. If the voltage is 28 volts or more, the
stator is OK. The rectifier-regulator is
faulty. Replace the rectifier-regulator.
If the voltage is less than 28 volts, the
stator is probably faulty. Test stator
further using an ohmmeter (test 3).
Battery
Continuously
Charges at
High Rate
2. Remove the connector from the rectifier-
regulator. With the engine running at 3600 RPM,
measure the AC voltage across stator leads
using an AC voltmeter.
3a. If the resistance is 0.1/0.2 ohms, the
stator is OK.
IF the resistance is infinity ohms, the
stator is open. Replace the stator.
3b. If the resistance is infinity ohms (no
continuity), the stator is OK (not shorted
to ground).
If resistance (or continuity) is measured,
the stator leads are shorted to ground.
Replace the stator.
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