7.6
Section 7
Electrical System and Components
Troubleshooting Guide
20/25 Amp Battery Charging Systems
When problems occur in keeping the ba ery charged or the ba ery charges at too high a rate, the problem can
usually be found somewhere in the charging system or with the ba ery.
NOTE: Always zero ohmmeter on each scale before testing to ensure accurate readings. Voltage tests should
be made with the engine running at 3600 RPM - no load. The ba ery must be good and fully charged.
Problem Test Conclusion
No Charge
to Battery
1. Trace B+ lead from
rectifi er-regulator to key
switch, or other accessible
connection. Disconnect it
from switch or connection.
Connect an ammeter from
loose end of B+ lead to
positive terminal of ba ery.
Connect DC voltmeter
from loose end of B+
lead to negative terminal
of ba ery. With engine
running at 3600 RPM, read
voltage on voltmeter.
If voltage is 13.8 volts or
more, place a minimum
load of 5 amps* on ba ery
to reduce voltage. Observe
ammeter.
*NOTE: Turn on lights, if 60
wa s or more. Or place
a 2.5 ohm, 100 wa
resistor across ba ery
terminals.
1. If voltage is 13.7-14.7 and charge rate increases when load
is applied, the charging system is OK and ba ery was fully
charged.
If voltage is less than 13.8 or charge rate does not increase
when load is applied, test rectifi er-regulator for proper
ground. Using an ohmmeter set to the Rx1 scale, check
the resistance from the rectifi er-regulator housing to the
ba ery ground. Resistance should be less than 1 ohm. As an
alternative, connect a jumper lead from rectifi er-regulator
housing to the ba ery ground and retest charging voltage. If
charge voltage measures 13.7-14.7 volts, the charging system
is functioning. If resistance is greater than 1 ohm or charge
voltage is less than 13.7, then re-establish ground between
the ground strap and mounting screw.
If voltage is less than 13.8 or charge rate does not increase
when load is applied, test stator (Tests 2 and 3).
If the voltage is low and does not increase, and there is no
charging/amperage output, disconnect and reconnect the
rectifi er-regulator plug and retest.
a. If the ammeter shows charge for a short time but then
drops back to zero, the rectifi er-regulator is functioning
correctly but the ba ery is faulty. Replace the ba ery.
b. If no amperage/charge rate appears during the retest, go
to step 2.
2. Remove connector from
rectifi er-regulator. With
engine running at 3600
RPM, measure AC voltage
across stator leads using an
AC voltmeter.
2. If voltage is 28 volts or more, stator is OK. Rectifi er-regulator
is faulty. Replace the rectifi er-regulator.
If voltage is less than 28 volts, stator is probably faulty and
should be replaced. Test stator further using an ohmmeter
(Test 3).
3a. With engine stopped,
measure the resistance
across stator leads using an
ohmmeter.
3a. If resistance is 0.064/0.2 ohms, the stator is OK.
If the resistance is infi nity ohms, stator is open. Replace
stator.
3b. With the engine stopped,
measure the resistance
from each stator lead
to ground using an
ohmmeter.
3b. If the resistance is infi nity 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 stator.
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