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Volkswagen Alternator

Earlier (mid 1973) aircooled Type 1 VWs used a lower wattage generator which worked fine for general VW use.  Later (mid 1973 on) Type 1 VWs used a higher wattage alternator.

A common electrical upgrade is to update a generator system to a newer alternator system.

There are also a lot of aftermarket alternator options.  Some of these are very low quality, while others may be as good as NOS Bosch versions and in some cases better.

Part Numbers

Aftermarket

Rebuilding a generator or alternator is actually a simple job that can be performed in a small shop with minimal special tools.  Be cause of these, there are may shops that rebuild alternators and can even rewind them by hand and produce a final product with higher output than he original units.  And like everything else in the aftermarket VW parts world - quality varies greatly.

Wrangler NW - 100 Amp Alternators

Generator Polarization

If you have a new generator or one that has been sitting around for a long time, it may not be magnetized and you will need to polarize it if you would like it to work.  Once polarized, it should stay magnetized for months unless defective.

To polarize a generator:

1. Remove the fan belt

2. ground the DF terminal on the generator to the generator frame

3. connect a wire from the positive terminal on the battery to the D+ terminal on the generator

4. The generator shaft should start to spin.  If it doesn't, your generator is defective.

5. Allow it to spin for just a few seconds to avoid overheating

6. Replace fan belt

7. re-test the generator voltage with the DF terminal grounded

8. If the output voltage is still low, the generator is defective

Note that alternators do not need to be polarized.  They use a trigger current from the alternator dash light to start the process of charging.  If the alternator light circuit is out, your alternator won't charge.

Alternator Pulleys

These come in many different forms and the stock black ones are generally the most dependable and work.  More on pulleys and fan belts is discussed in our Fan Belt Page.

Amperage

Pre 1973.5 Beetles were equipped with a 30 amp generator, which is just enough to run everything on a stock VW with just a tad extra for a small radio.  In 1973 VW added a fresh air box with a fan and upgraded the charging system to include a 60 amp alternator.  Other aftermarket alternators claim to produce more amperage than the stock ones.

Alternator Wiring

Earlier alternators used an external regulator and therefore had more external wires connecting to it.  Later alternators had less wiring.

Externally Regulated

Alternators requiring an external regulator have a B+ terminal and a triple terminal in the center top for three other wires that should be wired into a socket made for this triple terminal.

The triple connector has a red (D+), brown (D-) and green (DF) wire that connect to the voltage regulator.  The regulator has a forth blue wire (61) that connect to the alternator warning light.

A single larger red wire with a ring terminal should connect to the B+ terminal on the alternator.

Internally Regulated

Large red wire connects the battery to the B+ terminal

blue wire in the main harness goes to the D+ terminal.  This wire connects to the alternator idiot light and must be connected in order for the alternator to charge.

External Regulated to Internally Regulated Alternator

The larger red wire goes to the B+ terminal

The green wire should be connected to the blue (61) wire and the green wire can be connected to the D+ terminal.  The voltage regulator should be disconnected and can be removed if you like.

Testing an Alternator

• Check your battery with the car parked. A fully charged battery should be at 12.6 volts.

• Start your VW

• Check the voltage across the battery.  It should be at 13.5-14 volts at high idle if the alternator is working properly.

Double Alternators

It's been done.

Ref:

engine with double generator (photo)

 

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