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Library Home Page > 1st Generation (1983 to 1993) > Electrical
1st Gen Venture Charging System Testing
  Author: TAC
  Views: 14115     Votes: 17

 The 1st Generation (83-93) Venture charging system uses a permanent magnet type AC Magneto (ACM) alternator. The stator and rotor of the alternator are located inside the left engine cover. The rotor is attached to the crankshaft and contains permanent magnets. The stator coil is mounted stationary to the engine cover and is surrounded by the rotor magnets. When the engine is running, the spinning magnets around the stator coil create an AC voltage within the windings of the stator. The AC voltage produced by the alternator is converted to DC voltage by the Regulator/Rectifier (RR) which is mounted on the frame of the bike under the fuel tank which is midship in the chassis. The RR sends a regulated 14.5 volts DC to the bikeís electrical system and shunts excess voltage to ground.

Charging System Specifications:

Output: 14.5 Volts / 435 Watts / @ 5000 rpm
Stator Coil Resistance: 0.357 ~ 0.483 Ohm @ 68ļ F (20ļ C)
Stator AC Voltage Output: 100+ VAC* @ 4000 rpm

*The AC Voltage spec is not listed in the Yamaha factory service manual. Observed output is from known good systems. See test procedures below.

Test Equipment Needed:

Basic hand tools

A good digital Volt/Ohm Meter* with these capabilities:

  1. DC voltage up to 20V

  2. AC Voltage up to 100+V

  3. Diode Test Function

*Not all meters operate exactly alike. You should be familiar with your meter and understand how to operate it correctly to avoid misinterpreting the readings. 

Testing Charging System Output

Using your volt meter, read static battery voltage with all systems turned off. A fully charged battery should read 12.6 volts. If battery voltage is low, it should be charged before testing the charging system. A weak or defective battery may cause false test results. Have the battery tested or replaced if it will not achieve a full charge from a battery charger.

With a fully charged battery, start engine, turn off all electrical accessories. Read battery charging voltage as engine speed is increased to 2000 rpm. Charging voltage should be 14 ~ 15 volts. If the voltage is around 14 volts, the charging system is OK at this time. If you have been experiencing intermittent charging system problems, double check all connections in the system.

If the charging voltage is out of specs, check all connections in the system. This includes battery cables, RR connector, stator connector, and main fuse connection. All power to and from the battery must pass through main fuse connections, so don't forget to check these when diagnosing electrical problems. The main fuse is located on top of the battery.
An excellent check for tracing down bad connections is a voltage drop test performed at operating current flow. This is carried out by having mutlimeter on DCV with one probe on one side of a connector and the other probe on the other side so any poor or loose connection will produce a voltage reading which is the difference or voltage drop on that section.
If the charging system tests above 14-15 V at the battery at 2000 rpm...test the brown wire at the RR plug for voltage at the same rpm....if it is lower than the battery voltage...inspect the RR connector and the ignition switch connectors for a poor connection.  If the brown reference wire voltage is also high, check the ground wires (2 blacks) at RR plug and the negative battery cable connections are clean and secure as a good ground path is needed for the RR to shunt (or "dump") excess current to ground to control voltage. If all these checks find no problem, RR replacement is recommended.
The dash voltmeter on the 1st gen measures the voltage on the SIGNAL circuit, so if that is noted to read low and battery and reference voltages are normal, inspect the SIGNAL fuse clips for corrosion or lost tension.

Testing The Stator

Engine and ignition switch turned off. Remove the left chassis body panel to access the connectors.

This picture shows the view with the connectors labelled and unhooked for testing.

The connector from the stator has 3 white wires. Disconnect the connector and inspect the terminal pins for looseness, corrosion, or damage, and repair as needed. A poor connection will cause high resistance, heat and may have even discolored or melted the plastic. If you find a problem with this connector, it can be cut out and the wires soldered directly to each other to eliminate future problems with the connector.

Check the stator coil resistance by measuring at the three stator terminals of the connector "A" shown above. Set the meter to the lowest ohms scale and measure between pins 1~2, then pins 1~3, and finally between pins 2~3. All readings should be approximately 0.35~0.48 ohms. Note that some meters may not read accurately at this low setting so donít be too concerned just yet if you donít get the exact spec. Look for consistency between the 3 sets of readings. The specification is when the windings are at 68 F so colder temps will lower resistance, hotter temps increase it slightly.

Next, with meter set to a higher ohms scale (>100 ohms), connect one meter lead to a good engine ground and use the other lead to test each stator terminal for a short to ground. All should read open (OL) or very high resistance.

Check the AC voltage output of the stator. Bear in mind you are dealing with significant voltage and current, a shock could cause severe injury, Set your meter to read AC (NOT DC) voltage on the 100+ volt scale. Start the engine and read each pair of terminals in the same order as you did above, 1~2, 1~3, 2~3. At normal idle speed, voltage should be around 20~25 volts AC on each pair. Rev engine to 3000 RPM and read voltage on each pair again. Voltage @ 3000 RPM should be around 60 volts AC. All pairs should read equal voltages. If one pair reads significantly less than the others, or if all read significantly lower voltage than specified, the stator may be defective .

The rectifier outlet harness can now be disconnected (5 wires, 2 red, 2 black, brown) It is in close proximity to the stator plug.

Test the disconnected half of the connector "D" by testing for battery voltage (DCV) between the 2 pairs of Red and Black wires.

Turn key on, and test voltage between the Brown wire and should be battery voltage. Switch key off. This brown wire is the voltage input for the regulator to control the voltage..a poor connection causing low voltage input can cause the regulator to control at too high a system voltage, which can damage components.

*note....later 1st gens eliminated the brown wire, voltage was sensed at the regulator.

For the diode test, we use both the rectifier outlet connector "C" and the stator connector "B", so we are testing inlet and output wiring of the rectifier regulator. The diodes allow current flow in one direction but not the other.


Set the meter to "Diode Test" .

1. Attach red test lead to the Bat+ pin (red wires), touch black test lead to each stator pin (white) on the RR connectors. Each pin should read "OL" (open circuit) on the meter.

2. Attach Black test lead to Bat+ pin (red wire), touch red lead to each stator pin. Each pin should read about .5 volt. (my meter read 550 millivolts). Again look for consistent values of all 3 as meter accuracy varies.

3. Attach red test lead to Gnd- pin (Black wires), touch black test lead to each stator pin. Each pin should read about .5 volt.

4. Attach black test lead to Gnd- pin, touch red test lead to each stator pin. Each pin should read OL on the meter.

If any of these readings are not as specified, the regulator/rectifier is defective.

Last update: 10:17 AM Sunday, October 28, 2012

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