Converting a Volkswagen electrical system from six to 12 volts lets you enjoy brighter headlamps and a better charge at idle, among other benefits. Prepare your shopping list and have your tools ready, including a good lamp, a garage and perhaps a friend to help. You will use all of these to upgrade your system to 12 volts.
Park the Beetle on level ground and turn off the engine. Refer to the circuit diagram in the shop manual for your year and model Beetle. Use the masking tape and marker to identify and label wires going to all of the components you will replace. Inspect all wiring for broken insulation or damaged or loose connections. At damaged insulation, cover with heat shrink tubing. At damaged wire, splice in a new section and cover the exposed connection with heat shrink tubing. At damaged connections, remove the existing electrical tabs, strip 1/4 inch of wire and crimp new electrical tabs to match existing.
Remove and replace each component, working with one component or compartment at a time, beginning with the battery. Lift the rear seat and detach the negative and positive battery leads. Loosen any hardware securing the battery prior to replacement, using the ratchet set, wrenches or other tools as applicable. Remove the old battery and put in the new battery, but leave the new battery disconnected until the last step. Verify with the voltmeter that the battery holds a charge.
Remove all labeled wires from the voltage regulator, which is located next to the battery, and use the screwdrivers and sockets to replace the six-volt regulator with a 12-volt regulator. Reattach the wires correspondingly. Use a wire brush to clear away any rust or scale where the regulator is attached and verify a ground connection, using the voltmeter set to continuity testing. The regulator will typically have to be primed per the instructions that come with the part.
Label and disconnect the wires leading to the coil in the engine compartment. Loosen the clamp and nuts securing the coil and replace with a 12-volt coil. Tighten the clamps and nuts to secure the new coil and reattach the wiring.
Determine if your model Beetle comes equipped with a carburetor solenoid. Label the wires and remove. Use the socket or adjustable wrench to replace the six-volt carburetor solenoid with a 12-volt carburetor solenoid and reattach wiring.
Label and remove wires going to the carburetor choke coil (if equipped). Use the flathead screwdriver to remove the screws and hardware securing the choke coil and retain them for reinstallation. Replace the 6-volt choke coil with the 12-volt choke coil and secure it with the screws and hardware. Reattach the wires.
Label and remove the wires going to the generator with a socket and ratchet. Loosen and remove the air filter. Use the hex key to remove the generator strap. Use the socket to remove six bolts securing the generator to the fan shroud and remove this assembly. Hold the generator pulley in place with a screwdriver and loosen the loosen the front and rear generator pulley nut with a ratchet or wrench. Slowly remove the fan and then the pulley with the puller. Collect the Woodruff keys. Remove the fan shroud sheet metal with a socket or wrench from the generator. Install the new 12-volt generator by connecting it in the reverse order of how you removed the 6-volt generator.
Remove all six-volt fuses at the dashboard and replace with 12-volt fuses, according to the circuit diagram. Open the hood and remove and retain the electrical cover. Identify and remove wiring going to the dimmer switch. Replace the six-volt dimmer switch with a 12-volt dimmer switch. Locate the six-volt flasher and identify and label all wires attached. Remove the six-volt flasher and replace it with the 12-volt flasher. Reattach wires to the flasher. Locate and identify all wires going to the headlight flasher relay. Detach wires and remove the headlight flasher relay and replace in the same location. Reattach the wires correspondingly. Locate the positive power lead to the windshield wiper motor. Splice and connect the 12 to six-volt drop resistor. Secure the resistor to the car body as needed. Reinstall the electrical cover.
Open all light fixtures one at a time with a Phillips screwdriver to remove and replace all six-volt bulbs with 12-volt lightbulbs with wattage ratings as noted on the circuit diagram. Reinstall the light fixtures in existing locations. Remove the six-volt sealed beam headlamps with the screwdrivers and replace with twelve-volt sealed beam headlamps.
Locate the horn under the fender. Remove the rubber boots at the wiring and identify the positive and negative leads with masking tape labels. Disconnect the wires, and replace the six-volt horn with the 12-volt horn using a wrench or socket. Reconnect wires.
Place the car out of gear in neutral or park and chock the front wheels. Open the deck lid. Reach to the upper right and turn the 17 mm bolt counterclockwise with a box end wrench until it starts to turn. Note that this bolt holds the engine and the transmission to the starter. Remove the box end wrench and attach a vise grip so that it holds the bolt in place when you turn the nut from the other side. Crawl underneath the car and locate, identify and remove the wires going to the starter and solenoid. Locate the upper nut, held on the other side with the vise grip, and from underneath the car loosen it with a 17 mm socket and extension. Then loosen and remove the lower starter bolt. Use both hands to loosen and remove the six-volt starter and solenoid and replace with a 12-volt starter and solenoid. Retighten the starter bolts. Attach the battery cables to the new 12-volt battery. Attach all wires to the starter and solenoid to test the starter. Test the starter by completing the circuit with a screwdriver across the two big terminals to hear if it turns. Test the solenoid by placing the screwdriver across the battery connection to the solenoid connection, which should activate the solenoid and starter and crank the engine. Note that the engine will not start without the key in the run position. Detach the battery cables to continue the 12-volt conversion.
Remove the electrical housing from beneath the hood. Locate, identify and remove all wires going to and from the radio. Remove the radio with the screwdrivers and pliers. Replace with a 12-volt radio and reconnect and secure the new radio with pliers. Once you have completed this swap, you are ready to check that everything is connected, connect the battery and test out the benefits of your new conversion.
