Vintage VW Wiring Basics

This article was contributed to by Jeremy Goodspeed of The vintage Volkswagen community thanks you!

The basic wiring of a VW Beetle is very similar to many other types of European cars. Like most cars, with age, time and exposure, resistance can build up in a wiring harness and render simple circuits useless. So with basic understanding of European wiring standards, many repair tasks can be tackled. From the addition of a simple accessory to a complete wiring harness overhaul, following some simple rules will make for a successful repair.

First, we need to discuss a few basics regarding VW wiring. If you have spent any amount of time looking at a VW wiring schematic, you will notice that RED is used for constant power, meaning powered regardless of the ignition position, BLACK is switched power and BROWN is used for ground. The other colors will vary depending on the circuit but these three colors will cover most basic circuits. In addition to the color coding, a VW wiring schematic will have a number coding assigned to each terminal on a switch or other hardware component. These European terminal designations are also known as DIN standard and are used to determine a terminals use. First, take a look at the Bosch Terminal Designations.

These numbers are generally printed on the switch or other device for easy reference. As you work with DIN standard wiring, certain numbers will be seen more often than others. For example, a terminal designation of 30 always represents a direct connection to the positive battery terminal. While a terminal designation of 15 represents battery power when the ignition is in the crank or run position. As you become more familiar with DIN pin designations, you should be able to figure out the purpose without looking at a wiring schematic. Now when you combine the colors with the pin designations, you will notice a pattern. Red wires go to pin 30, black wires go to pin 15 and brown wires go to pin 31.

The next item you will notice on a VW wiring schematic is a number size assigned to every wire. The number wire size varies from 0.5 to 6.0. This refers to a European sizing that is measured in millimeter squared (mm²). European gauge wire is not easily obtained in America, so for replacement, it must be converted to AWG (America Wire Gauge). The conversion from European wire size to AWG is not exact. Using a slightly larger wire size is good assure against resistance and heat. For example a 1.0 mm² wire should be replaced with a 16 AWG wire which is 1.31 mm².

European to AWG Wire Conversion Chart

  • 20 AWG 0.51 mm²
  • 18 0.82
  • 16 1.31
  • 14 2.08
  • 12 3.31
  • 10 5.26
  • 8 8.36

Now that we have some wiring basics covered, the next task is to gather the proper supplies for a correct job. You may need some or all of the following: Solid colored stranded wire, stranded tracer wire (wire with a colored stripe), brass open barrel German electrical connectors with installation tool, junction connectors and PVC plastic sleeving. No one vendor supplies all of the listed items, so here is a list of vendors for your supply needs:

If your goal is to replace your entire wiring harness to factory specifications, you may decide a pre-made replacement harness as a good option. These harnesses fit good, wire colors codes are accurate and can be installed in about a day. Many VW vendors sell these, so see if this option is for you. Following either the instructions or a factory wiring diagram makes for an easy installation. However, if your vehicle is right hand drive or your goal is something custom, altered or improved, a custom made harness may be your best choice.

A custom made wiring harness will require much more time than a pre-made harness. It also requires an excellent knowledge of wiring and is not for the beginner. The vehicle pictured in the article needed some mild, but necessary changes. Our goal was to make these changes without losing the original factory look, being careful to follow the original DIN color coding exactly. This becomes vital for future repairs, especially if the vehicle is sold.

First, we needed to add grounds to all external light circuits. This is a very important step, as early VW’s use a body ground for these circuits. As we restore our cars, the mill thickness of paint diminishes the ability for the circuit to use the body ground properly. This results in poor lighting performance or sometimes an intermittent flickering of the effected light. Bright and reliable lighting is a very important item. Newer VW’s used ground wires instead of body grounds as this problem is prevalent.

Second, was to improve the quality of the headlamp illumination by adding two 40 amp 12 volt 4 pin relays. By adding a separate power lead for the headlamps and controlling them with a pair of 40 amp relays, you can eliminate the brightening and dimming of a headlamp that is caused with engine RPM. Understanding that relays are electrically controlled switches, we can use one relay to control both low beam bulbs and the other to control the hi-beam bulbs. Another feature is with a single separate 8 AWG power supply run directly from the battery to the relays 30 DIN power pin, you can also add higher wattage headlamp bulbs without overloading the system. Furthermore, by separating the power used for the headlamps from the headlamp switch, we were able to eliminate most of the amperage load and prolong the life of the switch. This info will describe the typical installation of headlamp relays.

For installation in a VW Beetle, please note the following. Pin 86 is easily drawn from the stock hi-low headlamp relay. Simply run the yellow and white wires from the hi-low relay to each 86 pin instead of the fuse box. Pin 87 of the relays then is connected to the fuse box like factory. Please note that pin 85 is used for ground. Why is a ground not PIN 31? Relays are used in many configurations, and pin 85 can be used as a negative winding end or a ground. This depends as to the purpose of the relay. In this case, it is used as a ground.

As you begin building your wiring harness, it is a good plan to have all your
hardware items, such as your fuse box, wiper assembly, switches and relays installed in the vehicle. This installation will aid in determining the length of wiring needed to complete a circuit. To help with the location of those numbered pins, take a digital photo of each item before installation into the vehicle. Simply refer to these photos for an easy reference. Many times these numbers are small and difficult to view from inside the dash area.

Building and installing a wiring loom can seem overwhelming at first. However, as you simply separate each wiring loom section it becomes easier to manage. The VW beetle has a main loom, left and right front lighting loom, and two short and simple tail lamp looms. Beyond these main looms, are short groups of wires between switches and relays. The main loom that spans between the dash and the rear of the car, have only 11 wires. I added two additional wires to power the headlamp relays and the electric fuel pump to this project.

To begin building the harness, make sure the lengths of wire is sufficient for the run. The main loom needs to be built outside of the vehicle. Take careful measurements so your loom is the correct length. I generally leave the wiring longer than needed so we can trim the length once the loom is installed in the vehicle. Once the length is determined, group the proper wires into a single bundle. Generally using a quality electrical tape every 12-18 inches will keep them strait and grouped. Once the wires are loomed into a proper group, slip the PVC tubing over the group. Next, install the main loom into the vehicle and adjust until it is located properly. Finally, we can trim the wires to proper length. Make sure to leave the wires long enough for maintenance. Then, install the brass open barrel electrical connectors. These connectors are identical to the factory connectors. Using the proper crimping tool assures a good connection. Now repeat this operation for each loom. Sometimes small and accessible looms can be pre built in the vehicle to determine length, removed for the installation of the PVC sleeving, and reinstalled for final fit. Be sure not to add any connectors until the sleeving is properly installed.

Be sure to test all wires once installed. Basic knowledge of an OHM setting on a multi tester is a must. Testing continuity is simple. Using your test meter set to an OHM setting, just place one test lead at one end of the wire, and the other test lead at the opposite end. An open or incomplete circuit will read as 1. A perfect wire will read as .000 the closer the number to .000 the better the continuity. On a 1967 and newer Beetle, this is a great way of testing the back-up light circuit before applying battery power. With the car in reverse, the switch will make contact and complete the circuit, and have a reading at or near .000. This continuity is what will turn on the reverse lights when 12 volt power is applied. While in any other gear, the switch does not make contact and is considered an open circuit, keeping the reverse light off. I also found using an OHM tester is especially important when determining the quality of ground points. I determined my ground points to be metered at .002, so when you consider the minor resistance within the body, this is a solid ground point.

Once the installation of all the wires is complete, it is time to test the system. Install all fuses according to the wiring schematic. Next, make all final connections, install a battery, and test. Test each item separately, headlamps, parking lights etc. I generally start with items that have consistent power. Once these items checkout, I will turn on the ignition to run position and test the switched items, such as turn signals and horn. If you have done everything properly, everything should work perfectly. If you have something not working properly, go back to the wiring schematic and double check every connection of the affected circuit. Generally you will find a wire or two that have been transposed. Once the correction is made, the item should work properly. If you have any fuses that immediately blow, please check that circuit for a short. An electrical short is generally a powered wire that is coming in contact with a ground.

With a basic understanding of wiring and some patience, European DIN wiring can be easy to understand and easier to repair. By removing wiring resistance and upgrading some circuits, your beetle will gain reliability and safety.

Posted by Eric Shoemaker

Hello, I'm Eric. I started Air-Cooled Artifacts (previously, and Lane Russell). I drive a '67 Beetle daily and love to share vintage Volkswagen stories with the world.

  1. Thank you for such a great article. I have a ’67 and am actually working on the wiring now. I’m printing this as a resource.

    1. Thank you very much for reading!

    2. I have a 1963 wiring nightmare any help would be greatly appreciate and pics of the back of the fuse panel and headlight switch

  2. This is a great read, and timely. Getting ready to refurb my generator on my ’67 and planning to go back to the OG push-on terminals rather than screw-on.

    1. Thanks Marius.

  3. This is really nice work. I plan on rewiring my bug soon. It’s a disaster and I’m not ever sure how it keeps working like it is. Much needed resource. Thank You

    1. Jeremy Godspeed gets all the credit for the article. I just put everything together.

  4. Thanks Jeremy. Your article was extremelly valuable

    1. Thank you for reading!

  5. I have a 66 with wires all over the place, about to rewire it…Thanks

    1. This article will help that for sure. Good luck!

  6. I accidently grounded the fuse relay block to the ashtray for a moment—– now the car is completely dead. did i destroy a relay? The ignition does nothing, no headlights etc. the fuses look okay– what have i done?

  7. I have a 1967 standard Beetle
    I accidently grounded the fuse relay block to the ashtray for a moment—– now the car is completely dead. did i destroy a relay? The ignition does nothing, no headlights etc. the fuses look okay– what have i done?

    1. Harry,
      I’d write Jeremy directly about this.

  8. This was an excellent article, this helped be out in the greatest way when doing my son’s 68 beetle.

    1. Israel,
      Thanks for reading! I’m glad you enjoyed it.

  9. i need full and clear electrical wiring diagram Volkswagen betel 1967 model.
    thanks for your support

    1. Good morning from Texas, Yohannes! You do not say where you are located. However, I want to point you to the following Link. Once you have opened the Link, scroll downwards to year 1967. You will see wiring diagrams for both non-USA and USA Beetles. Choose the appropriate one for your vehicle and enlarge so that you can view how it all works. I wish you well. Thank you for contacting! jay

  10. Hi, I re-wired my 67 beetle with a full wiring harness. I took photos from before to make sure I don’t stuff up with where everything goes. Then my phone got stolen and now I’m lost. But its just with the wiring of the starter and solenoid. Its my first time wiring a beetle. Please if you can help, I’d be really glad. Thanks, Devon.

  11. Have any of you seen this wiring system yet? I think it just came out, but looks pretty robust.

    1. Dave,
      I have not. This looks interesting. Some looks not “stock” which is a hmmm.. Jay, what do you think?

  12. If anybody out there needs a nice 205K distributor let me know. No charge but…..please just use it for your self and dont go ahead and sell it as it is a nice one. Most of the ones on samba are horrible and need reuilding and refinishing, not this one. I also found three 105 carbs in great condition and am having one rebuilt totally including bushings. Will let you guys know later. Spent many hours researching them and was quite interesting. It is weird to find out the 1967 bugs had multiple changes during the 1966 to late 1967. Two types of seats were found including the belt type and the type with the knob on the side of the seat to move it forward(found in later bugs). Have fun!

  13. Great write up. Thanks!

  14. I just finished rewiring my 69 vw bug. all new switches and volt regulator. hooked up battery which is fully charged and I get nothing at the Ignition Switch and nothing comes on. I have all 8 amp fuses installed and the previous owner had 5-8amps and 5-16 amp in the fuse box before I started rewiring. The vehicle ran fine up to that time. I need some help if possible and greatly appreciated.

    1. Please respond to me on my email address.

      1. Frank, Retrace all of your wiring and the connections. Also the voltage regulator needs to be checked as you are not getting power to the key or upfront. Make sure all is correct. If you have a voltmeter then it makes it easier but bugs are very simple and this means that something simple is not right. I changed the same on another bug but had no power either. Found out it was the voltage regulator(brand new) not wired right and also the fact that overnight it completely drained my battery to zero.

  15. Tim from Nashua, NH US of A January 28, 2018 at 10:32 pm

    Very nice article on the overall process. A couple question please. I have a 69 sedan, while a very pretty and operational car, many of the electrical connections appear to be corroded. Or at least not my level of perfect. Do you think my process below will improve and extend the circuits? Am I adding value or doing something bad.

    Disconnect the battery, methodically go to specific wire connection areas needing cleaning. I do one connection or wire at a time, I have used both vinegar and/or a CLR product (Calcium, Lime and Rust chemical. I paint the liquid on with a flux brush, wait, maybe use a brass wire brush, rinse with water, dry, then use a dielectric paste on both connection.

    I struggle with “if it aint’ broke – let it alone” and I can be a bit “frugal” .

    Any thoughts? Thanks for the article. Tim

    1. Hello, Tim…Wiring is wiring whether it is a ’67 or a ’69 Bug. I am happy to see your post. Cleaning terminals is something which I advocate. I DO hope that Jeremy responds. He is THE Master when it comes to wiring! For those of us who don’t have broken or burned wiring, I think that what you are doing is a responsible way to “renew” connectors. When people ask me about starting problems (for instance), I encourage them to begin at the battery and work their way through each connector–cleaning, renewing screws/bolts and washers and tightening. Usually this is sufficient to renew electrical service throughout the vehicle. And, don’t forget that ground strap from the transmission nose to the chassis! I throw this into the arena until Jeremy responds. Keep up the good work! jay

      1. Tim from Nashua, NH US of A January 29, 2018 at 10:22 am

        Thanks folks – While there is a wealth of information out in the InterWeb – very few sites are active with real humans- you are to be congratulated, THANK YOU.

        Granted, a wiring/clutch/carb issue and solution for a 1969 discussed and solved in 2002 is still a resource today in 2018. I am a-scared to post anything in – fear of !!!YOU LAZY NEWBIE — READ POST NUMBER XXX.XXX AND YYYY.YY and 10 other articles with initial false solution/brick walls then finally a good solution….. !!!!

        Please permit me a few tangents.

        My primary concern was my usage of vinegar/CLR product – I use this process (also electrolysis) on all my other tools(shovels and rakes) but these other tools are not electrical, foreign nor 49 years young. Are there other products more better-er?

        1. Good point about the battery strap. Over my bug’s prior life with the constant removal of the ground strap – the ground strap (ribbon) was about 50% connected. I am not a purist at this point so I just got a new cable cable rather than a real appropriate strap from AutoZone. (little plug for AZ (not employee nor any business relation)), their tool rental program is FANTASTIC! I had the classic frozen Rear brake drum, 36 nut rusted and 567 torque. I did not have all tools e.g. 1/2 inch 6 foot breaker bar and drum puller. I plan to use Autozone for all my consumables and minor parts.

        2. Related to the battery, does anyone know of a battery kill switch that allows removal of the key regardless whether the power is turned off. I have the Harbor Freight product but the key must be in place and sticking out to connect the system. I don’t expect to have many children jumping around the back seat none-the-less I don’t want the key (mounted in the KickPanel) to be kicked and broken.

        3. As a former corporate dweeb well schooled in processes to develop processes. I am surprised I can’t seem to locate a list(pdf) of all Bug circuits/devices/wires containing the device, appropriate Bentley Service Guide function code, Terminal code, Preferred AWG wire gauge, FactoryColor(s), FuseBlock(FB) spade(front is front, left to right) and maybe other stuff I don’t know? Why you ask? My handwriting is not so good, I want to print the info onto plastic laminated(for durability) double printed labels with a 1/2 inch of adhesive for wrapping around the wire. i.e.
        Code E Wiper Switch, 53a, 20-22awg, Black/Violet, FuseBlock(FB)1
        Code H, Horn Switch, 54, 16-18awb, Bk/W/G (Black/White/Green, FB1

        Any buried Mayan treasure somewhere – I don’t want to reinvent a Version 1.0 Square Wheel. :) :) Yes, I realize that each wiring diagram will be EXACTLY the same except for 13 differences.

        Whew! I told you, “I am here from Corporate – how may I help you?” Start the EyeBallRolling with tight belly muscles. Sorry but I type fast. tim,.,

    2. Do whatever makes you happy. Why ask everyone if it works for you. If you have the cash then replace the harness or parts of it like I did. Otherwise do your thing. Whatever you put into your bug goes a long way. Even if it does not add value to it, the work is needed so do it and get some satisfaction from just that.

      1. Tim from Nashua, NH US of A January 29, 2018 at 1:28 pm

        yes, you are correct – my fear I would use the wrong product that would not last a year or worst yet by using the acid I would melt the fuse box spade to be a micro connection i.e. .125 inch width. :):)

        Re the wiring harness, sure I could buy it. But with my other endeavors I would not be able to allocate the time to do it. i.e. a normal person doing harness work might take 8 hours whereas i would need to use a Franklin Monthly planner. I have learned in life, due to my ADD (and the H as well). I can eat a elephant in small bites over a month or so – however I could not eat the elephant in one weekend.

        Thanks for all the wonderful comments – I LIKE this site! It is now time for me to leave my computer and start doing trash, toilets, termites and tenants. tim,.,

  16. Hello,
    recently purchased a 67 (very excited). Looking to get the wiring in shape… it’s poor. Looking at this article is great. relays are zip tied and jerry rigged. Looking at these pictures. Is there a mounting bracket available for relays?

    Thanks so much for the article and site.

  17. What color is this car?

    1. L639 Zenith Blue.

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