Ac Output Test; Tri-Circuit Alternator; Alternator Output Test; Diode Test - Briggs & Stratton 405777 Series Manual

6. If diode tests OK, check stator for bare wires or other
obvious defects. If grounded leads are not visible, re-
place the stator.
RED
LEAD
"A"
RED
WIRE
"B"
Fig. 14 − Testing Diode
NOTE: Service replacement diode harnessers are avail-
able. Use Resin Core solder when installing new harness.
Use shrink tubing or tape all connections. DO NOT USE
CRIMP CONNECTORS.

AC Output Test

1. Insert RED test lead into
2. Insert BLACK test lead into
3. Rotate selector to
4. Attach RED test lead clip to AC output terminal, Fig. 15.
RED TEST CLIP
TO AC OUTPUT
PIN
Fig. 15 − Testing AC Output
5. Attach BLACK test lead clip to engine ground.
6. With engine running at 3600 RPM output should be no
less than 14 volts AC.
7. 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.
8
TSM
receptacle in meter.
receptacle in meter.
(AC volts) position.
BLACK TEST CLIP
TO A GOOD
GROUND SURFACE
NOTE: Some equipment manufacturers supply the diodes
as an integral part of the equipment wiring harness.
Some equipment manufacturers use a 1 OHM 20 WATT
resistor placed in series with (+) 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.

Alternator Output Test

1. Insert RED test lead into
2. Insert BLACK test lead into
3. Rotate selector to
4. Attach RED test lead clip to output terminal, Fig. 16.
RED TEST LEAD
TO AC OUTPUT PIN
(GREEN CONNECTOR)
Fig. 16 − Testing Alternator Output
5. Attach BLACK test lead clip to engine ground.
6. With engine running at 3600 RPM, output should be no
less than 28 volts AC.
7. If no output or low output is found, replace stator.
8. If alternator output is good, test diodes located in wiring
harness.

Diode Test

NOTE: One diode is for the charging circuit and the other
diode is for the lighting circuit.
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."

Charging Circuit (Red Wire)

receptacle in meter.
receptacle in meter.
(AC volts) position.
BLACK TEST LEAD
TO A GOOD GROUND
SURFACE