Welcome to the BugShop FAQ

The text following is part of a series of articles written by John S. Henry on the restoration and maintenance of air-cooled Volkswagens. While his experience is exclusively with the Beetle, many of the techniques can be applied to other models.

This text is copyrighted and duplication, re-distribution or publication is prohibited without consent of the author.

Article: Understanding Your Starter
Last updated: 11/1/01

Understanding Your Starter

Symptom: Your 6 (or 12) volt bug sometimes doesn't start, you have worn through the sole of your sneakers pushing the car to start it and it is not "cute" anymore.

Before we start, this article requires that you either have a decent understanding of current and voltage, or have read the "Volts, Amps and Waterwheels" article in this FAQ.

The "hard start" problem is most prevalent in 6 volt Beetles, but can exist in 12 volt systems as well. In either case, you should know that this "hard start" relay fix (detailed below) is a Band-Aid for a less-than-perfect electrical system. I hesitate to even mention it. I am a purist and believe that things should be left "as they were" and kept in pristine condition through your dedication and loyalty. But I also know that on a cold December night, when you just want to get home and the snow is starting to stick, I can take my "dedication and loyalty" and shove it. I would say though, that you shouldn't do this for 12 volt systems as whatever problems that are causing it are much more easily fixable than with the 6 volts systems.

How it is Supposed to Work

You turn your key and electricity from your battery goes to your starter, which is just and electric motor, and it spins the engine. Any questions? At the high level, it is really that simple. The problems come in the way the electricity is delivered to the starter. But before we go there, lets make sure we understand how a starter works.

We have already established that it is just an electric motor, but there are two other things attached to it that you should know about:

Gizmo #1: The "bendix". For some reason I think "bendix" is one of those old words that you only hear your grandparents use. Like "housecoat" or "rubbers" (those rubber things that you supposedly put over your shoes when it rained). But most seasoned mechanics still call it that. The bendix is an electromechanical device that slides the little gear on the end of the motor shaft out so it can mesh with the teeth on the flywheel. It is attached directly to the starter. Without a bendix, the gear would have to be engaged on the flywheel all the time, even after the engine was running, and would make that noise that your grandmother's car makes when she "restarts" the car after it is already running (a noise that could bring you grandfather out of a coma).

Gizmo #2: The "solenoid". The solenoid is pretty much another name for "relay" in the case of the starter. It is actually an electromechanical device that pulls a set of contacts together to make the high current connection between the starter and the battery.

Ever hear someone crank a car until the battery dies? Errrr, errrrrr,,er,,er, then just "click....click" as they turn the key? That "click" is the bendix/solenoid working but there is not enough juice left to actually turn the engine over.

Now in most starters the bendix and the solenoid are the same electromechanical device. "Electromechanical" means that it takes electrical energy and makes mechanical movement out of it. The same coil (that produces a strong magnetic field) that throws out the gear, also pulls together the contacts. Cool, huh?

Lets talk about what a relay, and in the case of the starter, the solenoid does. Such a device allows a small amount of current to switch a much larger amount of current. The starter in your Beetle is, by far, the highest current device. Much more than the headlights, rear window defroster, radio, etc. all put together Starters can pull in excess of 100 amps from the battery; but fortunately for the battery, only for a brief period of time. Notice how fat that wire that goes from the battery to the starter is? You wouldn't want to pull that huge wire all the way up to the dash where the starter switch is and back again to the starter. One, it would be very cumbersome, and two, your starter switch could never handle switching that much current. That's what the solenoid does for you. It keeps that very high current circuit as short and direct as possible, just between the battery and starter.

So when you turn your key at the dash, you are actually applying battery voltage to the solenoid, which is then throwing the gear out to the flywheel and making a direct contact between the battery and starter via that big, fat wire.

That is how it is supposed to work.

Problems with the Starting Circuit

Relatively speaking, that solenoid itself, is a pretty high current device. I don't know for sure, but I bet it is in the 10 amp range for the 6 volt systems. So that circuit, from the battery to the dash, through the ignition switch and back to the solenoid, is a pretty high current one. This means that it is very susceptible to voltage drops. And the solenoid, especially after it is 30 years old, is pretty picky about voltage. Loosing 1 volt out of 6, and that coil just ain't gonna pull. Sometimes you hear about a "hot start" problem. Poor connections, as a result of corrosion, may drop varying levels of voltage depending on the temperature of the connection. And remember that passing current through a corrosive, resistive connection generates heat in that connection.

The "hard/hot start" problem is usually based in the solenoid (secondary) circuit, not the high current starter (primary) circuit. But don't overlook the obvious other connections (see below)

Here is some text and graphics describing the various starter circuits over the years.

1954-August 1959

In most of the 50's model years, the circuit was the same as the '61-'65 below, except that the connections to the headlight switch and fuse box were after the ignition switch (not shown here). From a current optimization (to the starter) standpoint, that made the most sense.

August 1959-1965

The dash is fed by a big red wire that comes straight off the regulator on the generator and goes directly to the light switch, from a "shared" terminal on the light switch, this wire goes to one of the fuses and from that same side of the fuse, it also goes to the ignition switch. A black wire goes from the ignition switch to another fuse, but from that same (unfused) side of the fuse, a black wire goes back to the ignition coil. NOTHING in this whole starting and ignition circuit is fused! Be careful. Another red wire comes off the ignition switch and travels all the way down back to the the starter solenoid.

Note that this secondary starting current path "touches" many components unrelated to the starting circuit (headlight switch, fuse box), but doesn't actually go through them. This is just done to optimize the wire path and provide voltage to other stuff along the way. Unfortunately though, it provided more connections for potential voltage drops.

1966

A fat red wire comes right off the starter lug that the battery wire is connected to and goes straight to the ignition switch. The "start" lead from the ignition switch then goes to a fuse end, from that same side, it goes to the headlight switch, "through" the headlight switch via another tab to the generator lug, then to the solenoid connection on the starter. This "moved" the ignition switch a little farther ahead in the circuit, but the switched lead than still had to pass along the headlight and generator circuits before getting to the starter.

1967-1968

The 12 volt system(s). They finally got it right. A lead came right off the battery, to the regulator (now located under the back seat), then up to the headlight switch, then to the ignition switch and then straight back to the solenoid.

1969-1971

Almost the same as above, except the current passed "through" the headlight switch (in one terminal, out another; instead of "piggy-backing" the same terminal) before going to the ignition switch.

After '71, the wiring diagrams get too complicated for me to follow anymore.

Stuff to Check First

Before you go running out to buy a relay, you should definitely check out your whole starter wiring circuit. First, the starter itself.

Most Beetle starters actually supply the voltage to the solenoid via the starter armature. This means that dirty or worn starter motor brushes can cause the intermittently dead starter problem too. It is really not all that hard to take the whole starter out and do a quick clean up on it. It may cure the problem all by itself. To do this, remove the starter from the car and remove the end cap on the starter (the end opposite the gear) by taking out the long bolts and remove the end cover. Clean up the brushes (a can of carb cleaner works well) and make sure that they are not worn down so much that they aren't making contact with the armature commutator. Replace them if necessary. Clean the commutator with a fine emery cloth or sandpaper (the copper "strips" on the armature shaft that the brushes ride on). Clean the thin slots between the commutator pads using and old toothbrush. Put some grease on the armature shaft end prior to re-assembling the end cover and some on the snout of the starter (shaft in front of the gear) before putting it back in the tranny.

Now, I can't possibly cover all of the details of all of the years of the Beetle's wiring (some in the diagrams above), so let me make some generalizations. In the list below, "good" in terms of connections, means clean, shiny and tight. Some connections are big eyelet, stud and nut type; many are .250" "spade" push ons; and some of the very old VWs had tiny screw terminals on everything. Get some fine sandpaper or emery cloth (I have a little, cheapy, rechargeable battery powered "Dremel" type tool, that turns much slower than a Dremel and takes all of the 1/8" shank accessories. I use it a lot for cleaning up contacts) and make sure that all of you metal contacts look like metal. Remove all corrosion and rust. Sometimes those female push on connectors get loose and you need to slip them off and squeeze them down a bit with some pliers to make them push back on snug. Sometimes you will need to replace connectors that are useless.

And let me diverge and talk about wire terminations in general. I am a bit fanatic about this. I do not believe that anything less than what I do is futile, but I do ALL of my wire terminations the same way: solder and heat shrink. I don't crimp anything. Yeah, I have the crimp tools and all, but something in my mind says that stripping a wire, slipping it into a barrel ended crimp type connector and then flooding the cavity with solder is the best way. A piece of heat shrink over the outside of the barrel, and a bigger one shrunk around the whole outside of the female push on, is what I do. Takes more time, but I feel better about it.

So here's what you should check:

Your battery terminals. Very often overlooked. Go buy on of those $2 battery terminal post cleaners and clean up the posts and the terminals, both of them. But leave the ground one disconnected until you have done ALL of the work on you electrical system.

The rest of the primary starter circuit. Follow those fat wires to where they go. The big fat red one usually goes right to the starter and is held there by a big eyelet and lug. Might be a bit difficult to get to, but crawl under and reach up. You might want to replace that cable, you can usually find them at Wal-Mart or your favorite local department store in a usable length. Make SURE that you have disconnected the battery ground when you do anything with this wire. It is not fused and if you short it you will get a crash course in welding and fire prevention. Also check the battery ground. It is usually either a fat black wire or a webbed copper strap and must have a very good, clean connection to the body of the car. Remember that current for everything that your battery powers passes through this cable. It should be the fattest pipe in the whole circuit (read the "Volts, Amps and Waterwheels" article). But leave it disconnected from the battery until you have everything back and are ready to test it out.

And lastly, the starter ground. "What starter ground?" you ask? Well, let's see, the starter is metal and it is bolted to the tranny, what could be a better ground than that? Well, what is the tranny bolted to? Rubber engine mounts, duh! Yes, the tranny must be grounded. Usually this is done via one of those braided copper straps up on the front tranny mount. It goes between one of the tranny-side bolts and one of the body-side bolts. It is subject to lots of abuse riding along under the car, all exposed. There has been much wailing and gnashing of teeth for overlooking this one.

The secondary circuit. Now this is where the variances between years comes in. In the older models (most all 6 volt) a thick (about 8-10 gauge) red wire carried voltage up to the dash and basically powered everything else (refer to the diagrams above). In some years, this wire came right off the battery under back seat, in others, it came from the voltage regulator mounted atop the generator back in the engine compartment. Then it either went straight to the headlight switch or it went to the fuse panel. But in all models, there is one main "feed" wire that supplies power to all non-starter devices. It is usually pretty easy to spot as it is thick and red. In 12 volt systems, it comes right of the regulator under the left side of the back seat. Check the connections that this wire makes at either end. They must be shiny, clean and tight. [In my '68s and '67, I spliced a blade-type fuse holder into this wire right off the battery. I think I used a 50 amp fuse in there. I never liked the idea of such a fat wire running unfused off the battery. You can get these high current fuses and holders a most autoparts stores]

Connections to the ignition switch. In the "metal dash" years ('67 and older), this is pretty easy as the back of the switch is easily accessed. But on the newer ones, it is embedded in the steering column with the turn signal/hi-beam switch, and it may seem a bit more complicated. Just look for that bundle of wires coming out of the steering column and up under the dash. You should be able to sort out the turn signal, hi beam and ignition switch ones by looking where/to what they go. Again, good, tight, shiny connections are needed.

The ignition switch itself. I have had these go intermittently bad in my cars. The switch itself is actually a separate component of the key mechanism on most newer ones, and should still be readily available. A real simple way to rule out the switch as the culprit is to just jumper it behind the dash at "that time" when the car won't turn over. Just use a good 14 gauge or better piece of wire. Jump from the "hot" side of the switch over to the terminal which goes down back to the solenoid. If it kicks over that way, but not when you turn the switch, it is probably a bad switch. Oh yeah, make sure it isn't in gear when you do this.

Another good way to trouble shoot the whole secondary starting circuit is to eliminate it by bypassing it with a jumper. If the car doesn't start and the battery seems to be good, make up a fat jumper wire (I have a few with some big alligator clips on the end) and jump between the positive terminal of the battery and the solenoid terminal on the starter. In doing so, you will have eliminated the entire secondary circuit with your jumper wire. If the engine turns over, you have verified that there is a problem (disconnect or voltage drop) in the secondary circuit. If it still doesn't, either your starter is bad, the battery is dead (even with a very weak battery, you should hear the bendix clicking) or the ground path between the battery and starter is bad (battery ground, starter ground).

The "Hard Start" Relay

Ok, so you thoroughly checked out the whole ignition system and if your starter leaves you stranded one more time you are probably going to do some irreparable damage to your Beetle.

We already have two circuits to talk about in the stock system:

The primary starting circuit. This is the 100-or-so amp, fat wire directly between the battery and starter, and the battery and starter grounds.

The secondary starting circuit. This is the 10 or so amp circuit from the battery to the ignition switch and back to the solenoid.

The "Hard Start" relay is about placing a new relay in the back seat/starter area and creating a third circuit. This new circuit would allow the ignition switch to only have to switch a low current relay, which in turn would switch the solenoid, which in turn switches the starter. It may sound a bit kludgy, but it does work. Rather than keeping up a voltage drop plagued solenoid circuit, you can greatly reduce the current through you "front to back" path between the starter switch and the starter by installing this relay. These relays will usually draw l amp or less. And remember, voltage drops are directly proportional to the current through the circuit; the less current you draw through a circuit, the less susceptible you are to voltage drops.

A simple relay has 4 or 5 contacts and is represented by this:

The "coil" connections are where you apply voltage to make the relay close it's contacts. The relay doesn't care which one you ground and which one you apply 12 volts to, it will work either way. [unless you find one of those old metal cased kind where one coil wire is tied to the metal case and hence to ground]

The contact terminals do just what the graphic indicates; when the coil is energized, the magnetic field pulls the moving contact down. Some relays have a "normally on" contact meaning that it makes contact while the coil is not energized, and breaks contact when it is. You won't use this connection on the relay if it has one. Most relays will have a graphic similar to this on the packaging.

Here's how you hook it up:

First, disconnect the ground from the battery, if you haven't already
Figure out where and how you are going to mount your relay. My suggestion is under the back seat somewhere.
Disconnect the wire from the solenoid connection on the starter, this would be the smaller wire. Bring that wire into the back seat area and connect it to one of the "coil" terminals on the relay. If you have an old metal cased/grounded relay, this wire should go to the "+" of the coil.
Ground the other "coil" terminal of the relay. You will have to make up a wire for this, a small eyelet secured with a sheet metal screw into some body metal is best. But not into the floor (will start rust). You might also use a nearby body bolt.
Now connect one of the contact terminals goes to solenoid terminal on the starter. You will need to make up another wire for this and is should be at least 14 gauge.
Lastly you will need to connect the other contact terminal to a battery source. You can tap right off of the battery's positive terminal, or from the "hot" (large) lug on the starter.

Some preparation work will pay off. After you read these steps, go scope out the whole deal in your car if you are going to do it. Take some measurements, then go buy all the stuff. You will need to find a 6 volt relay, and these may be a bit hard to find. The contacts should be rated for at least 10 amps at 12 or 6 volts DC (if the max contact amperage is rated at a higher voltage, it should still be at least 10 amps). Get the wire that you need. You need to make up 1) a ground wire for the relay coil; 2) a wire to go from the relay to the solenoid and 3) a wire to go from the relay to a power source. Buy the connectors that you need, most relays have the common 1/4" push on terminals. Heat shrink tubing will make for a nice installation and a soldering iron is needed too. When you are done, it should look like this:

And that is really all there is to it. Again, this is a Band-Aid, but one that many 6 volt VWs lived with for many years. It does work on the 6 volt bugs, but it really is not needed on the 12 volt ones. The problem is not nearly as common on the 12 volt Beetles and just getting all of the circuits clean and tight will almost always fix the problem.

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