Service Manual

Part Numbers
113476, 78-0060
Purpose
This gauge indicates engine speed.
How It Works
The tachometer measures the number of rotations of the crankshaft by
monitoring the B+ terminal of the voltage regulator. The alternating current
produced by the alternator allows the circuitry to “count” the revolutions,
then deflect the meter movement appropriately. Keep in mind that this
tachometer does not key off the ignition coil, but rather the charging coil.
Testing
1. With the tachometer still connected to the harness, start the engine.
2. Using a known good electronic tachometer or “Vibratach”, determine
the actual engine speed. Compare it to the tachometer in the
equipment.
3. If they are not within 10%, check for loose connections, a bad stator, or
flywheel magnet.
4. If no problems are found, the gauge must be replaced as it is not
serviceable.
Part Numbers
78-0030
Purpose
This gauge indicates the voltage across the battery.
How It Works
The meter movement moves proportional to the voltage level across the
two terminals of the battery. This is accomplished by placing a resistor in
parallel with the meter movement.
Testing
1. With the meter still connected to the harness, turn the key to the “run”
position.
2. Verify the conditions in the table. If they are not met, replace the
voltmeter, as it is not serviceable.
Gauge
Tachometer
Gauge
Voltmeter
Terminal Condition
I 12 volts DC ± 20%
G 0 volts DC ± 20%
Table 1
Glossary
GLOSSARY
3-10 Demystification Guide