Crossed Wires
Understanding VW Electrical Systems and Rewiring Fundamentals
By Ryan Lee Price
Photography: Ryan Lee Price
Do your headlights look dim? Does that little light on your speedometer not work? Did you even know there's supposed to be a little light on your speedometer? Not surprising, but, over time, most electrical systems fail. Dust, water, age, corrosion and the adverse elements cars face every day take their toll on its wiring. More than likely, if your car has never been rewired, it's overdue for one. For safety sake (i.e. burning to the ground), comfort of being able to read the warning lights on the dash (i.e. so it doesn't burn to the ground) and the convenience of seeing the map at night when you're lost are reasons enough to revamp the wiring in and around your VW.
With the backside of a Beetle's dashboard easily accessible from under the hood, electrical service, if deemed difficult from an enthusiast's point of view, is at least convenient to reach. Regardless, the majority of the connections can be made easily without having to remove too much of the car's equipment.
For a complete wiring harness replacement, first things first, disconnect the battery so the new harness won't be inadvertently damaged by a crossed "hot" wire during the installation. To make it easier to reach certain connections (the brake master cylinder and the rear tail lights, license plate light, etc.) the engine and gas tank need to be removed as well.
Since we are installing a pre-assembled harness from Wiring Works (via The Real Source) for a 12-Volt 1967 Beetle (minus a radio), all of the correct wires are accounted for (though some of the colors have changed from stock over the years). However, during the installation, you'll need to snip and reattach the slide connectors on a few of the wires, so proper tools are essential. Among standard screwdrivers, pliers, electrical tape and a utility knife, you'll also need wire/insulation cutters, spray silicon, slide connector pliers and a voltmeter. You shouldn't have to cut any of these wires to adjust them for length and proper connection. They are all pre-measured and pre-assembled for you.
Most important thing to remember when you're working with wires and electricity is to be patient. If the wires don't fit, don't force them. If you feel you have to yank, twist or crimp, you're probably doing it wrong. You need to be organized and plan ahead. Get a copy of the schematic for your car (visit www.vintagebus.com) and study it. Since it is a graphical representation of what's hiding behind the dash, it is neither to scale nor accurate to the position of the components (See Page 58). If all else fails, ask a professional for help, like we did. Rafael Gutierrez, master auto electrician at West Coast Classic Restoration, has seven years of VW wiring under his belt, and he showed us a few tips to make the job remotely comprehendible. On Page 63, we've also included a mini guide to purchasing new electrical components if yours have had it.
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Look at all of these wires. Don't get nervous when you open up the box. Each wire has a purpose and a meaning. See "What Do All These Wires Mean?" on Pages 57 and 59 for details.
When removing the old wires components, make note of how they were connected and where they go. It is easier to replace something if you know what was there before.
Before yanking out the main harness (from the engine compartment through the firewall to the voltage regulator under the back seat), cut off all of the extra wires on the old loom (tail lights, license plate light, etc.) and lash the new main harness tightly to the old one with electrical tape (make sure no loose wires are sticking out that can get snagged on the firewall). Get a friend to help pull the old harness out while you feed the new one through the hole. It is important not to lose the connection through this conduit.
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This same process must be done for the dome light harness as well, so the connection will not be lost between the dome light through the A-pillar to the fuse box in the trunk and door jam switches.
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Once the main harness is through, begin in the engine compartment by attaching the taillights with the taillight harnesses. On the right, the white wire/red stripe (in the black insulation--#32) attaches with the running lights via a plastic double connector and goes to the license light.
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The taillight wires are color coded as well: Black is for brakes, red is for turn signals and white is for the running lights. Make sure when you attach them to the taillight housing, make note of which bulb the wires are powering.
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The red (#2) and green (#12) wires will be attached to the generator, while the black wire (#7) goes to the ignition coil and the blue wire/green stripe (#10) is for the oil warning light.
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Remove all of the electrical components (fuse box, switches and relays, as well as the wiper motor and anything that might get in the way). Clean all of the components with electrical cleaner or a solvent. Make sure they are totally dry.
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While the components are drying, feed the other end of the main harness up under the dash and into the trunk. Be careful not to snag any wires along the way. Tuck in the wire along the base of the door sill, which will later be hidden by the carpet. Once in the trunk, take inventory of the wires splayed out before you and study the schematic to decide what goes where.
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Start with the furthest wires and work in. On the left headlight harness, feed the black/red stripe wires (#17 &18) into the hole in the body on the right above the gas tank and down to master brake cylinder. There are four wires, two for negative and two for positive.
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Along with the master cylinder brake wires go the wires for the horn (black/yellow stripe #16 and brown ground #19). Wire #38 is feed through the steering column and attached on the tab at the base of the column, leaving the exposed end of the wire underneath the horn button.
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Also on the left headlight harness are the wires for the left headlight (yellow #13, white #14 and the brown ground #20). These feed into the headlight bucket and are weatherproofed via a supplied rubber grommet. Use the silicone spray to ease these wires through the rubber grommet. The ground wire is attached to the body inside the trunk with a Philips screwdriver, while the other wires' ends are attached to the headlight socket housing.
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Wait until all of the wires are in place before you attach the socket housings. White (#14 & #21) in the left sockets of the housing, yellow (#15 & #22) in the middle and brown (#20 & #23) in the right for both headlights.
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Also on the left side are the wires for the left turn signals (gray #29 and black/white stripe #30). Black with a white stripe will always be on the left, while black with a green strip is for the right. To make it easier, each of the wires' connectors need to be clipped off before feeding them though the rubber grommet to the turn signal housings (use the silicone spray again). Once through, reattach the slide connectors with slide connector pliers.
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Start with the fuse box and work out. Each post of the fuse box has a specific wire assignment, and if they are done methodically and in order, there is very little chance for error. Start with the peripheral wires (i.e. from the headlights, turn signals and engine compartment wires, etc.) and work in, then attach all of the control switches. (See diagrams on Page 62)
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For the slide connectors in the double connection holders, use a pair of needle nose pliers to ensure a tight fitting. There's nothing worse than a faulty wire because of a careless fit.
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The dome light wires (red #25 and brown #24) attach from the dome light itself through the A-pillar to the door jamb switches. The brown wire is draped across the top of the trunk and will eventually run under the glove box, while the other half of the red wire (#26) is connected from the fuse box to the flasher relay.
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A voltmeter is used to test the proper function of various parts. For example, use it to make sure the relay switches are carrying proper currents to operate the high-beams, the dashboard dimmer switch and the turn signal relays and to make sure the wiper motor is in optimal shape. If something isn't functioning up to par, replace it.
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The rest is down hill from here. All of the major components are returned to their rightful places and the appropriate wires are reattached into their corresponding connections (see diagrams below). Keep organized and double check each wire's connection before moving on.
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After everything is properly connected, reattach the battery (after cleaning the posts) and go through the system, checking each function individually at first and then together as a system.
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Now Where Do I Go?
How the System Works
The six- or 12-volt wet storage battery (1967 and later have 12-volt systems) feeds current to a solenoid which engages the flywheel teeth and directs current to the starter motor. To recharge the battery after the system (including lighting and accessories) has drained its power, the engine-driven generator (or alternator) creates a charge that is fed back to the battery via the regulator, which adjusts the amount of returning current.
The stock Volkswagen electrical system follows a scheme common to European cars known as a "Bosch" system. The difference between European and American cars is centered around the use of relays. Until recently, American cars only used relays for a few accessories (headlights, horn, etc.), while the "Bosch" system requires them for most all wiring configurations.
There are two types of relays, electro-thermal and electromagnetic. An electro-thermal relay operates equipment based on a given interval of heat. When this heat reaches a certain level, the relay cuts off the current. After cooling down, the switch again closes. An example of this method is employed by the turn signals. The best feature of this type of relay is that a minor amount of current can switch major power on and off. An electromagnetic relay uses current to magnetize and move a mechanical plunger, much like on the starter solenoid and the carburetor's valve jet.
What Goes Where?
The surrounding diagrams are based on a 1967 Beetle and represent the various under-the-dash components that can be found in most aircooled Beetles. The wire connections are color coded to the appropriate colored wire and show the location of each wire based on the component. As well, the wire number in each diagram corresponds to the charts on Pages 57 and 59. For example, Wire Number Three in the "Ignition Switch" diagram is the red wire with the black stripe that comes from the starter and fits into the ignition in the upper left post as shown.
If you have any doubts about a component's durability, it is best to replace it with a new one
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