Service Manual

Part Numbers
57-9430
Purpose
The regulator/rectifier prevents battery boiling by shutting off the current so
that the battery sees only positive current and voltage (see Figure A).
How It Works
The voltage level across the battery is very near constant because the
battery has very low impedance (Figure B). This regulator/rectifier, like
many others, must be connected to the battery to function. Once the
voltage level of the battery has surpassed 13.6 to 14.5 volts, the voltage
regulator shuts off all current and no charging takes place (Figure C).
When the voltage again drops below the specified level, the voltage
regulator turns the current back on at the rated amperage of the alternator.
Testing
Check the battery before checking the regulator/rectifier for proper
operation. The battery must be fully charged and in good condition for the
regulator/rectifier to operate properly.
Refer to Table 1. Start the engine and check the regulator/rectifier output by
measuring the battery voltage at the battery terminals with a voltmeter. If
voltage is within that specified in Table 1, the regulator/rectifier is good. If
the DC voltage is greater than that specified in Table 1, replace regulator/
rectifier. If D.C. voltage is less than that specified, shut the engine off.
Examine all wires for loose, corroded, broken connections, short circuits,
etc. Check fuses. Make certain all circuits are complete from regulator/
rectifier B+ terminal to the battery positive terminal; and the battery
negative terminal is properly grounded. Start the engine and check D.C.
voltage again. If the D.C. voltage is still less than that specified, test the
alternator. If the stator is good, replace the regulator/rectifier.
Part Numbers
KH10215
Purpose
The regulator/rectifier prevents battery boiling by shutting off the current
when the battery has reached 14.7 volts.
How It Works
The voltage regulator rectifies the current so that the battery sees only
positive current and voltage (see Figure A). The voltage level across the
battery is very near constant because the battery has very low impedance
(Figure B). This regulator/rectifier, like many others, must be connected to
the battery to function. Once the voltage level of the battery has surpassed
14.7 volts, the voltage regulator shuts off all current and no charging takes
place (figure C). When the voltage again drops below the specified level,
the voltage regulator turns the current back on at the rated amperage of
the alternator.
Regulator/Rectifier
(20 Amp)
(Onan)
Regulator/Rectifier
(Kohler)
Test Reading
Primary coil resistance
1.0 Ohm
Secondary coil resistance 9.5 K Ohms
Battery voltage 12 to 13 Volts DC
2.5 amp stator resistance
0.33 Ohms
20 amp stator resistance Appriximately 29 volts AC @ 1800 RPM
Approximately 57 volts AC @ 3600 RPM
20 amp stator resistance 0.10 to 0.19 Ohms
Regulator/rectifier output 13.6 to 14.7 volts
Table 1
Glossary
GLOSSARY
Demystification Guide 3-15