When the ignition is turned on, voltage is supplied to the excitation winding of the generator (terminal "D" of the generator 9412.3701 and "B" of the generator 371.3701) through the control lamp in the instrument cluster (the lamp is on) and the resistors connected in parallel to it
After the engine starts, the excitation winding is powered by additional diodes of the rectifier unit (the control lamp goes out).
If the lamp is on after the engine starts, this indicates a malfunction of the generator or its circuits. The "minus" of the battery must always be connected to the "ground" of the car, and the "plus" - to the "B+" terminal of the 9412.3701 generator (terminal "30" - generator 371.3701).
Reverse connection will lead to breakdown of the generator valves.
When the generator is running, it is not recommended to disconnect the battery (especially on engines equipped with an injection system).
The resulting voltage surges in the on-board network can damage the electronic components of the circuit.
The generator valves (and other devices in the on-board network of the car with the generator connected) should be checked under a voltage of no more than 14 V, a higher voltage (for example, when checking with a megohmmeter) can cause damage to the valves.
If it is necessary to check the insulation of the windings with high voltage, the generator should be removed, and the winding terminals should be disconnected from the rectifier unit and voltage regulator.
Checking the generator
Start the engine, let it run for a few minutes, then press the gas pedal to bring the crankshaft speed to 3000 min –1 .
Turn on the high beam headlights, rear window heating, and heater fan.
Measure the voltage at the battery terminals, which should be higher than 13.2 V for the 9412.3701 generator and 13.6 V for the 371.3701 generator.
If this is not the case, the voltage regulator with the brush assembly, the generator windings (open or short circuit) are faulty, or the contact rings of the excitation winding are oxidized.
To make sure that the voltage regulator is working properly, turn off all consumers except the high beam headlights and again measure the voltage.
It should be within 13.2–14.7 V for the 9412.3701 generator and 13.6–14.6 V for the 371.3701 generator.
The removed voltage regulator of the 9412.3701 generator can be checked by connecting a lamp (1–5 W, 12 V) between the brushes, and a power source (only direct current, “minus” to “ground”!) to the “D+” and “ground” terminals, first with a voltage of 12 V, and then 15–16 V.
In the first case, the lamp should light, in the second - it should not.
If the lamp lights up in both cases, there is a breakdown in the regulator, if it does not light up, there is a break or the contact between the brushes and the terminals of the regulator is broken.
In both cases, the regulator should replace.
To check the generator regulator 371.3701, the current source should be connected to terminals "B" and "C" ("plus") and "ground" ("minus").
To check the rectifier block valves, disconnect the wires from the battery, generator and from the terminal(s) of the voltage regulator. Connect the battery "plus" via a lamp (1–5 W, 12 V) to the "B+" terminal of the 9412.3701 generator (to the "30" terminal of the 371.3701 generator), and the "minus" to its body.
If the lamp is on, then there is a short circuit in both the "positive" and "negative" valve blocks.
To check for a short circuit in the "positive" valves, connect the battery "plus" via a lamp to the "B+" terminal of the 9412.3701 generator (to the "30" terminal of the 371.3701 generator), and the "minus" to the terminal of one of the stator phase windings. If the lamp lights, one or more positive valves are broken.
To check for a short circuit in the "negative" valves, connect the "plus" of the battery through the lamp to the terminal of one of the phase windings of the stator, and the "minus" to the generator housing.
If the lamp lights, one or more negative valves are broken or the stator windings are shorted to the generator housing.
To exclude a short circuit in the windings, remove the generator from the car and, having disconnected the windings from the voltage regulator and rectifier unit, check their short circuit to "ground" with a lamp or ohmmeter.
The generator valves can also be checked with an ohmmeter, without connecting the battery and test lamp.
The short circuit of additional diodes can be checked by connecting the "plus" of the battery through the lamp to the "D" terminal of the 9412.3701 generator (to the terminal "61" of the generator 371.3701), and "minus" - to the terminal of one of the phase windings of the stator (to one of the mounting bolts of the rectifier unit).
If the lamp is on, one or more additional diodes are broken.
A break in the main valves is determined by a sharp decrease in the output current (voltage drop under load).
This can also be caused by a break or short circuit in the generator windings.
A break in the additional valves can be determined by low voltage on the "D" plug of the 9412.3701 generator or the "61" plug of the 371.3701 generator (below 14 V) at low and medium rotation speeds of the generator rotor.
Definition The serviceability of each diode (main or additional) can only be checked on the removed rectifier unit using an ohmmeter or test lamp.
If the rectifier unit fails, it is recommended to replace it as a whole.
Individual valves can be replaced, but the main valves will require re-pressing in the holder - an operation that requires accuracy and skill.
The stator and rotor windings are checked with a special flaw detector or electronic oscilloscope - according to the shape of the voltage curves.
Possible malfunctions and methods for eliminating them
Cause of malfunction
Remedy
The control lamp does not light when the ignition is turned on
The control devices do not work
- Fuse F19 in the mounting block has blown
Replace fuse
- Open circuit in the instrument cluster power supply circuit:
Do the following:
- - no voltage is supplied from the mounting block to the instrument cluster;
- - check the "O" wire and its connections from the mounting block to the instrument cluster;
- - no voltage is supplied from the ignition switch to the mounting block
- - check the "GP" wire and its connections from the ignition switch to the mounting block
- - The ignition switch does not work
Check and replace the faulty contact part of the ignition switch
The indicator lamp does not light when the ignition is turned on and does not light when the engine is running.
The indicator lamps are working.
The battery is discharged
- The indicator lamp has burned out or the contacts are not tight enough lamp sockets are pressed against the printed circuit board
Replace the burnt-out test lamp, bend the contacts of the lamp socket or replace it
- Open circuit in the circuit between the instrument cluster and the generator "D" plug
Check the "KB" wire and its connections from the generator to the instrument cluster
- Worn or stuck brushes, oxidation of the contact rings
Replace the brush holder with brushes, wipe the rings with a napkin soaked in gasoline
- Damaged voltage regulator (open circuit between the "DF" terminal and "ground")
Replace the voltage regulator
- Disconnected wire from the "D+" terminal of the brush holder
Reconnect the wire
- Short circuit in the positive valves
Replace the rectifier unit
- Unsolder the excitation winding terminals from the slip rings
Solder the terminals or replace the generator rotor
The control lamp is brightly lit or dimly lit when the engine is running. Battery is discharged
- Generator drive belt slipping
Adjust belt tension
- Voltage regulator is damaged
Replace voltage regulator
- Rectifier block valves are damaged
Replace rectifier block
- Excitation winding power diodes are damaged
Replace diodes or rectifier block
- Excitation winding terminals are unsoldered from slip rings
Solder terminals or replace generator rotor
- Open or short circuit in stator winding, short circuit to ground
Replace generator stator
The control lamp lights up when the engine is running. Battery is overcharging
- Voltage regulator is damaged (short circuit between terminal "DF" and "ground")
Replace voltage regulator
Increased generator noise
- Generator bearings are damaged
Replace rear bearing or front cover with bearing
- Interturn short circuit or short circuit to "ground" of stator winding (generator howl)
Replace stator
- Short circuit in one of the generator valves
Replace rectifier unit
