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Electrical Tµ¼Ê or your VW· there are no ghosts in there!
By Keith Park
Who hasn't had an electrical problem with their VW? Not many because
as our systems get older moisture and salt take their toll on the
connectors and the brass gets brittle with age and can break.
Ill keep this brief as all you need to know is stated in Ohm's law:
V=I*R
Resistance multiplied by current equals Voltage. Therefore voltage divided
by current is resistance and current equals voltage divided by resistance.
There is one other piece of theory to memorize· current flows THROUGH a
conductor or wire and voltage is the potential ACROSS it (between the wire
and ground). In other words voltage is the energy between the conductor
and ground that pushes the current through. For example 6 amps is the
amount of electricity flowing through a wire and 12 volts is the amount of
energy across it to allow it to flow.
Why is everyone whining about the old 6Volt systems?? Because when the
connections are made or patched improperly or are simply old and dirty
there is less voltage to push the current through and according to ohms law
there is twice the current than a 12 volt system uses to run the same
things.
If a connector for a 10 amp 12 volt wiper motor develops a resistance of .2
ohm because it's dirty it will have a voltage drop across it of 2 volts.
This will slow the wipers a little but on a 6 volt system the current
required for the same wiper motor will be 20 amps and the .2 ohm dirty
connection will have a drop of 4 volts and with only 6 to begin with will
bring the wipers to a stop. So, simply put, the 6 volt systems require you
to keep everything up to spec more than the 12 volt systems do, they wont
let you get away with sloppy connections.
Volt-a-drops, these are simple power resistors that are used in
series with the 6V part. They are fine if the part only uses a steady
current and you have a lot of extra power to throw away. Since it's a
fixed resistor and according to ohms law if the current drawn by t©“š e
changes so does the voltage drop across the resistor and therefore the
voltage across the device, say, for instance, a wiper motor which draws
different currents at different speeds and different loads. This doesn't
work very well and in order to get a voltage drop of 6V across the
resistor you need a resistance equal to that of the device being used which
the same as connecting 2 of these devices up, not a very good idea with the
limited power output of our generators. There are DC-DC converters out on
the market that convert much more efficiently but they are very expensive
for the larger current models.
Generator to Alternator conversion. This is a good idea but not
usually necessary. The Alternator produces AC as opposed to the generators
DC output. Alternators all have the AC rectified to DC before it reaches
the output terminal because all cars use DC. Alternators are much more
efficient and tend to hold up better at slower speeds where generators fall
apart but if you convert be sure to use an alternator with a large enough
output to make it worth while. Our generators output 30A so you will want
an alternator of say 50A or more. This is only really necessary if your
running all kinds of lights and a 1000W sound system or something like
that. On my Square I have halogen fog lights, power windows, a good sound
system, and other electrical goodies all over it and I still run a
generator and have no problems. I get 20K out of the generator brushes and
9 years out of the last battery so I won't convert and most people don't
need to.
Grounds! This is the culprit of most of the "Strange" electrical
problems. If a ground connection is off or a high resistance the current
will look for the next path of least resistance and that may be through
some other electrical part that isn't even supposed to be on at the time.
You can find a ground path through a lightbulb and the current flowing
through the bulb will light it, perhaps only dimly, and send you looking
for another problem soU÷Ý A major offender in the type 3 is the fuel
gauge cluster on the older cars. They are only grounded through the spring
clips and that is just not reliable. When the gauge ground opens up all
kinds of weird things start to happen when the power looks for other paths
to ground through the fuel gauge and other warning lights. The early fuel
injection grounds on the heads were also nasty salt exposed culprits. So,
when you are looking for that strange problem that seems to be affecting
multiple things make sure everything is grounded. On the VW's ground wires
are always brown so make sure everything brown is grounded. Check with an
ohmmeter.
What to do about those nasty pre-68 ignition switches. If yours
still works it wont for long and the availability of new ones is almost
non-existent. They were under designed and the 6V ones all took a real
beating switching the 60A or so the 6V solenoids took. The repair is a
relay, a relay being a set of high-current contacts that are operated by a
magnetic coil that draws very little current. Connecting that coil between
the switched output terminal for the starter (Terminal 50) on the ignition
switch and ground energizes that coil every time the starter is selected
and it only draws a half amp or so, so the contacts will last forever.
Connect the high current contacts of the relay between Terminal 30 ( or any
B+ high current feed) and the wire feeding the starter solenoid. The relay
will then handle the current switching for the solenoid. If your switch is
still working now do this and it will stay that way, if its not it may be
rebuildable but when rebuilt, depending on how bad the damage was, it may
not be able to properly switch the high current and require this relay.
This just touches on a couple common problems with the type3's. Keep
in mind that VW was very good at using the same color wires for the same
circuits over the years as well as the same terminal numbers. If the
wiring diagram for your year is black and white then look at a<MŒQ ear
that is color and you can figure out most of the colors used in the B&W
versions.
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