Checking the charging circuit (VW Golf 1)

Security measures

When performing any work on electrical circuits associated with a generator, it is important to follow these rules:

1. Never disconnect or rearrange the battery cables while the generator is running, otherwise the rectifier and/or voltage regulator may be damaged. It is not advisable to make any connection or disconnection in the charging circuit while the engine is running.

2. Never allow the generator to rotate with the power cable disconnected if the excitation windings are under voltage from the battery; otherwise the rectifier diodes may be damaged.

3. When connecting wires to the battery, always carefully observe the polarity of their connection - if connected incorrectly, the semiconductor devices of the car will be damaged (in particular, rectifier diodes). It is recommended to connect the positive (+) cable to the positive (+) battery terminal first, then the negative (-) cable to the negative (-) terminal.

4. Always disconnect the battery ground before connecting the charger to isolate the alternator from the battery and external charging equipment. The charger should be connected to the battery in parallel (positive battery terminal to the positive terminal of the charger, negative to the negative).

Verification procedure

1. Make sure that the alternator drive belt is tensioned correctly (see chapter "Car maintenance work"). The battery must be in good condition, its terminals, as well as other connections and wires of the charging circuit must be clean, securely tightened and provide good contact.



2. Check the vehicle's electrical system for leakage current, which can discharge the battery while the vehicle is parked and make charging difficult. Disconnect the positive cable from the battery and connect an ammeter between the cable and the positive terminal of the battery. With all electrical devices disconnected, (clocks, interior lighting, headlights, etc.) the ammeter should show a current of no more than 10 mA. If the current is large, find out and eliminate the cause.

3. Disconnect the wire connectors from the rear of the alternator, then connect the negative terminal of the voltmeter to ground and turn on the ignition. Connect the other terminal of the voltmeter to each of the disconnected wires of the alternator in turn. If there is no voltage on the blue wire coming from the indicator lamp on the instrument panel, check the discharge indicator lamp circuit and the lamp itself.

4. If there is no voltage on the main (red color) charging circuit power wires going to the starter, check the wires and electrical connections between the battery, starter and generator.

5. If no fault is found, check the generator output current under load as follows:

Disconnect the connectors and install a jumper between the blue wire and its terminal on the generator. Connect an ammeter between the power (red) wires and their contacts on the generator. Connect a voltmeter to the battery terminals. Connect a resistor between the positive battery terminal and the "ground" that provides a load current of 30 A in the circuit (figure D:1). With the engine speed at 3000 rpm, headlights, heater fan and rear window defroster on, the generator output current should correspond to that specified in section "Technical data".




To ensure the required generator power, the voltage between the battery terminals should not fall below 13 V. If the voltage is low, check the voltage regulator in the following order:

6. With the engine speed at 3000 rpm in the circuit assembled according to the diagram in Figure D:1, adjust the load resistance so that the generator output current is 25 A (generator 35 A), 30 A (generator 45 A), 35 A (generator 55 A) or 45 A (generator 65A). If the voltage regulator is working properly, the voltmeter reading should be between 12.5 V and 14.5 V. If the regulator does not provide the specified voltage, replace it.

7. Check the voltage drop in the positive branch of the charging circuit as follows:

• Assemble the test circuit as shown in Figure D:3. Run the engine at 3000 rpm and turn on the headlights. If the voltmeter reading is greater than 0.5 V, the positive branch of the charging circuit is faulty.
• If the positive branch of the charging circuit is OK, check the voltage drop on the negative branch.

Assemble the circuit shown in Figure D:2. If the voltmeter readings exceed 0.25 V, the negative branch of the charging circuit is faulty - check the connections of the battery and the power unit to the "ground".

NOTE: Most problems with the battery charging system are caused by worn alternator brushes or a faulty voltage regulator.

The procedures for replacing the brushes and voltage regulator are described in this chapter. It is recommended that more complex faults be repaired by an auto electrician. It may be more economical to install a new generator assembly than to purchase individual parts and repair the generator.

CAUTION: To avoid damage to semiconductor devices, ALWAYS disconnect the battery before starting any work on the electrical system.