Volume 7 - VW Electrical Basics
As we all know, Ferdnand Porsche designed an awesome automobile but I don't think he ever expected it to last as long as it has. Lets face it, most of our VWs are 25 to 45 years old, many suffer from poor quality repairs at some time or another in their life. This article will show the novice owner how to identify and hopefully repair the different electrical circuits found in the classic VW automobile. I plan on following this up with an electrical primary designed to teach the novice owner basic electrical principals needed to use this information to fix their car.
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4. Distributors
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VW used two basic systems in their automobile. The 6v systems found in the early VWs up through 1966 and the 12v system that is still being used today. What does this mean? Well, the if you have an older (pre 1967) VW that hasn't been converted then you are stuck with trying to find bulbs, battery's and electrical components that are almost obsolete. The owners soon realized this and converted many of the earlier VWs to 12v. If you have a newer (1967 and up) VW then this isn't an issue. I won't go into the conversion process here because it's covered numerous places on the web but just know that it's not too expensive and fairly easy to do if you're mechanically inclined. The other significant improvement VW did to the electrical system was the switch from generator to alternator in the early 70s. Gone were the days of the lights that got brighter or dimmer depending on engine RPM. Unfortunately, with the demise of the generator went the ability to push start a VW with a totally dead battery. As you've probably noticed, VW uses fuses that are unlike anything found on american cars. Yes they are getting harder to find but they're cheap and work pretty well as long as everything else electrical is working correctly. When it's not, you'll know it from the fireworks show under your dash. Think of your wiring harness as the car's central nervous system, it's a bunch of wires going everywhere. If you've ever looked under your hood at the dash you know what I mean. Hopefully Bubba hasn't been there before you "fixing" things, it he has, your work is cut out for you. The German Engineers in their infinite wisdom came up with a method to make sense of this jumble of wires. By using a combination of wire color coding and terminal designators you can determine each wire's and every connection's purpose. Here are some color code basics:
Below is an example of some terminal designations and wire color coding for a 66 and 67 Type 1.
Click here to open a picture of this wiring harness. (this is a large 1.6 Meg file so it will take awhile) I've shown you some basic wiring colors and designators. Open the above link for the wiring diagram and lets follow the ignition circuit from the battery to the ignition coil. This is the circuit that gets energized causing your sparkplugs to fire when you turn on the key. You will have to switch back and fourth between this discussion and the picture to follow this circuit. 1. 12 volts DC is available from you positive battery terminal via the B+ terminal on the voltage regulator and terminal #30 on the headlight switch to terminal #30 on the key switch through a large red conductor or wire. 2. When the key is turned on, 12 volts DC is supplied from the key switch terminal #15 to the RH fuse (looking a the rear of the fuse panel from the hood area) on a black wire. 3. At that point, the circuit is bridged to the adjacent fuse location, a black wire carries the voltage from the fuse panel (same side) and travels through the harness to terminal #15 on the ignition coil. From this point it's bridged over to the electric choke and the idle control valve on the carburetor. Note: since the wire exited the fuse panel from the same side, this circuit isn't fused, ie: protected by a fuse. As you can see, the circuit is fairly easily traced through the harness on the diagram. To physically trace the circuit, you just need to know it's connection points. On this circuit it's the battery, B+ on the regulator, #30 on the headlight switch, #30 on the ignition switch, the RH two fuse locations and terminal #15 on the ignition coil. The US Navy uses a method of troubleshooting called Half Stepping. Lets say you suspect your ignition isn't getting the required 12 volts. To apply Half Stepping to this circuit you first need to confirm that the voltage is in fact missing (eliminate the obvious, make sure your battery is ok, check the B+ on the regulator since it's easily reached). Once that is determined to be good, turn on the key and check for 12 volts at terminal #15 on the ignition coil (the end of the circuit). If it's not there, we half step. Go half way back in the circuit and check for 12 volts. In this situation, I'd check terminal #15 on the key switch. Depending on your reading, you'll have just determined if the problem is in the first or second half the circuit. If terminal #15 on the key has 9~12 volts, the problem is after that. Conversely, if it doesn't have the required voltage, check back further. Just with what you've learned so far and a couple of simple pieces of electrical test equipment (Test Light and Digital Volt Meter) you can isolate most common electrical problems. The VW ignition system in it's standard form is very simple. Consisting of an electrical source (car's battery), timing control (distributor) and spark amplifier (ignition coil) it's the basic system used throughout the world before electronic ignition became the norm. The problem with this system is it's inability to deliver a very hot spark and the fact that it relies on ignition points to fire the plugs. In the VW engine, the sparkplugs must fire in a very extreme environment, a cylinder's compression runs between 100 and 160 pound per square inch, the combustion chamber temperature can run between 0 and 500 degrees and the carburetor "may" be supplying the correct amount of fuel. I say may because each of those variables changes the amount of fuel required. Now lets add contact points to this set of variables, points, work well when they are clean and properly adjusted. This holds true for about the first 1000 miles after replacing them. Almost immediately the points start to burn and go out of adjustment changing the timing or point where the sparkplugs fire. This vary reason caused modern auto manufactures to switch to high energy ignition systems that don't rely on points. A high energy system almost guarantees that the plug will fire no matter what conditions exist in the combustion chamber. They also consistently fire at the right timing because instead of points, they now use electronic systems with no contact, electrical arcing or wear items. The system was good in 1965 but let's face it, by today's standards, it's out of date. You're probably thinking, my whole car is out of date, yes it is, but it should still run good and your stock ignition system is probably causing it not to whether you know it or not. You're thinking, heck my car runs well right now, why should I change. They say ignorance is bliss, that's definitely true when it comes to upgrading your ignition system. The typical VW will benefit from faster starts, smoother idle, better gas mileage and a possible increase in performance depending on the condition of your current system. At an absolute minimum, I recommend a points replacement unit. First, let's get rid of those troublesome points. There are 3 common replacement systems for VW points, the Accufire, Compufire and Pentronics units. These are not electronic ignition systems, they are points replacement units. Cost for these units run between $35 and $70, it's money well spent. Imagine, never replacing your points, once you set your timing, theoretically it will stay the same for years.
A Pertronix points replacement system. Next it's on to high energy ignition systems. A high energy ignition system typically consists of a "Brain" and a high output ignition coil. These systems range in cost from $80 for a very basic unit without a coil to several hundred dollars for complete systems. I'm not going to go into the various units here but our club's links page has many vendors offering these units. The high energy ignition is where you start to see the increases in mileage, smoother operation and better starting. A distributor is the funny looking round thing below your carburetor with all the fat wires coming out of it. What does it do you ask? The distributors job is to send spark out to the various cylinders at the correct time. It's really the heart of the ignition system and as such, it can make a big difference in how well your VW runs. There are three variables here, the type of distributor, it's condition and where it was built. Distributors are categorized by the type of advance they use. Ignition advance is a mechanism built into the distributor to adjust the timing while running to compensate for engine speed and load on the vehicle (hills etc...). Vacuum Advance Distributors - The Vacuum advance distributor has been around about as long as VWs have. There are probably 50 different types over the years but luckily for us, most VW parts are interchangeable. You engine doesn't know that your distributor is out of a 68 Super Beetle, it doesn't care. You can tell if you have a Vacuum Advance by checking if there is a large round canister hanging off the side of your distributor. It will have a hose running up to the carburetor from the canister. This is the distributor of choice for the stock VW. As I mentioned before, they compensate for engine RPM, throttle position and load on the vehicle. Centrifugal Advance Distributors - these are also known by their model numbers such as the 009, 010, and 050 with the 009 being the most common. These units advance the timing based on engine RPM only. While this is good for racing applications, it falls far short of the needs of a street automobile. A centrifugal advance distributor cannot compensate for load and throttle position, it's strictly based on engine speed. If your VW has an annoying flat spot just off idle, it's probably got a centrifugal advance distributor in it. They are cheap, commonly available and since VW and Porsche put them in their high performance engines, everyone thought it would be good for their regular VWs, wrong. Unless you have a high performance engine, a vacuum advance distributor will run better in your VW. Condition - The condition of your distributor can have allot to do with how well your car runs. Usually if it's bad, the spark will jump around excessively or the advance will not be working. Since this happens gradually, you probably won't realize it. Like I said, ignorance is bliss. If you are checking your timing with a light and the mark is jumping around so much you can't tell where it is, then your distributor is pretty much shot. Also if you go to rev it up while watching the mark, it should shift as the advance comes in, if it doesn't, you may have a bad vacuum canister, frozen advance mechanism or the vacuum hose has a leak. Where they are built - What does it matter where your distributor was built? Anymore it doesn't really because almost all new VW parts are built in Mexico, South America or the Far East. German ignition components are getting hard to find and if you do, you won't have any trouble selling them. That's because replacements from the places mentioned above typically have quality control issues. Two identical parts can run completely different and many are marginal at best. This holds true for most replacement VW parts these days, look for German stuff if you can find it. Replacing your distributor - New replacement distributors come in two basic flavors, centrifugal advance (009) for about $59 and the Vacuum Advance (called an SVDA) for around $100. Don't worry, there are plenty of used distributors available, just check E-bay or TheSamba. And that's all I have to say about that! Chris R. |
This club is not affiliated with or endorsed by Volkswagen AG or Volkswagen of America, Inc. All Volkswagen trademarks herein are used under license from VWoA.
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