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Article: Understanding Your
Last updated: 11/1/01
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 #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.
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
Here is some text and graphics describing the various starter circuits over the years.
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
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
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.
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.
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
So here's what you should check:
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.
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 secondary starting circuit.
This is the 10 or so amp circuit from the battery to the ignition switch
and back to the solenoid.
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:
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.
Copyright© 1998; John S. Henry