Diode Test; Ac Output Test; Tri-Circuit Alternator - Briggs & Stratton Twin Cylinder L-Head Repair Manual

7
6. With engine running at 3600 RPM output should
be between 2 – 4 amps DC.
a. Output will vary with battery voltage. If battery
voltage is at its maximum, output will be
approximately 2 amps.
7. If no output or low output is found, test diode.

Diode Test

In the Diode Test position, the meter will display the
forward voltage drop across the diode(s). If the voltage
drop is less than 0.7 volts, the meter will "Beep" once
as well as display the voltage drop. A continuous tone
indicates continuity (shorted diode) An incomplete
circuit (open diode) will be displayed as "OL."
1. Insert RED test lead into
meter.
2. Insert BLACK test lead into COM receptacle in
meter.
3. Rotate selector to
4. Attach RED test lead clip to point "A" and BLACK
test lead clip to point "B," Fig. 17. (It may be neces-
sary to pierce wire with a pin as shown.)
a. If meter "Beeps" once, diode is OK.
b. If meter makes a continuous tone, diode is
defective (shorted). Replace.
c. If meter displays "OL," proceed to step 5.
5. Reverse test leads.
a. If meter "Beeps" once, diode is installed back-
wards.
b. If meter still displays "OL," diode is defective
(open). Replace.
6. If diode tests OK, check stator for bare wires or
other obvious defects. If grounded leads are not
visible, replace the stator.
"A"
RED
WIRE
"B"
Fig. 17 – Testing Diode
NOTE: Service replacement diode harnesses
are available. Use Rosin Core solder when
installing new harness. Use shrink tubing
or tape all connections. DO NOT USE
CRIMP CONNECTORS.
8
receptacle in
(Diode Test) position.
RED
WIRE

AC Output Test

1. Insert RED test lead into
meter.
2. Insert BLACK test lead into COM receptacle in
meter.
3. Rotate selector to V~ (AC volts) position.
4. Attach RED test lead clip to AC output terminal,
Fig. 18.
5. Attach BLACK test lead clip to engine ground.
RED TEST CLIP TO
AC OUTPUT PIN
BLACK TEST CLIP
TO A GOOD GROUND SURFACE
Fig. 18 – Testing AC Output
1. With engine running at 3600 RPM output should
be no less than 14 volts AC.
2. If no output or low output is found, replace stator.

TRI-CIRCUIT ALTERNATOR

The Tri-Circuit alternator provides alternating current
through a single output lead and connector to a wiring
harness containing two diodes.
One diode rectifies the AC current to 5 Amps –
(negative) DC for lights. The second diode rectifies the
AC current to 5 Amps + (positive) DC for battery
charging and external loads, such as an electric clutch.
NOTE: Some equipment manufacturers supply
the diodes as an integral part of the
equipment wiring harness.
A 1 Ohm 20 Watt resistor is placed in series with the (+)
DC charging lead, limiting the charging current to
approximately 3 amps when the clutch is not engaged.
When the clutch is engaged the resistor is bypassed
allowing full output to the battery and clutch.
NOTE: The 1 Ohm 20 Watt resistor is supplied by
the equipment manufacturer.
The battery is not used for the lights, so lights are
available even if the battery is disconnected or
removed. Current for the lights is available as long as
the engine is running. The output depends upon
engine RPM, so the brightness of the lights changes
with engine speed.
receptacle in