On Wed, 4 Jun 2003, jon wrote:

> With all this talk of "relaying" headlights, I have a couple of questions.
> My 1983 diesel vanagon has a "power shortage" in the front of the van. The
> lights dim when the fan comes on, the stereo freaks out sometimes when the
> head lights are on, etc.
>

I have this exact problem in my '82.  I'll try to remember to share
anything I come up with with you, and I'd appreciate it if you'd do the
same. :)

I'd initially blamed poor grounding, but that seems to be only a small
part of the problem.  I connected a digital voltmeter between the negative
battery post and the shell of the cigarette lighter (the handiest ground
point on the dash).  I got about 0.30 volts difference with the headlights
and blower fan on -- more than I'd like, but only about a third of the
total drop I'm seeing.  I plan to try cleaning the main wiring connections
on the back of the fuse panel to see if that helps.

I have a voltmeter wired into one of the switched circuits up front, and
with the headlights on I lose about a volt...brake lights cost me about
half a volt...turn signals another half volt when they're lit...radiator
fan is another volt...  Clearly this is just intolerable.  I plan to clean
and tighten all the stock connections first (it can't have been this bad
from the factory, can it?) and then perhaps start using a seperate,
heavy-gauge wire and relayed circuits for the high-drain stuff.

> 1) Why relay? Does the light switch not handle enough current? Or, is this
> a relay that controls a seperate power line to the headlights?

Yes, and yes. :)

> 2) Would install another (or thicker) power wire to the front solve this
> voltage drop problem? (Yeah, I could use the wire resistance tables,
> length,  and total current draw to figure out the voltage drop with Ohms
> law...but it's more fun to ask the list
> :-) )

That's in my plans eventually, but I suspect most of the voltage drop I'm
seeing is at connectors, not in the wire itself.  It can't hurt, though,
since VW seems to use wire about one size smaller than I'd usually
consider prudent for everything.  Ever noticed that skinny little wire in
the engine compartment they figure is good for the 48-amp glowplug
circuit? ;)

David Brodbeck, N8SRE
'82 Diesel Westfalia
'94 Honda Civic Si