[T3] Non-Working Headlight

[Dave Hall]

I had something a bit similar when repairing a Beetle battery connector.  I
had bought an aluminium one with screws that clamped onto the wire.  I
thought it would be helpful to fill the gap with solder, and warmed it up
with a blow-torch, then filled the gaps with solder.  It worked fine for a
couple of weeks, then produced a high resistance at the connector.  I
replaced it with a brass one which worked properly.   I assumed some sort of
electrolytic action had oxidised the aluminium casting.  Obviously normal
solder wouldn't have bonded to the aluminium (which naturally has an oxide
layer on it anyway), but something changed in the contact between the
aluminium and the copper wires. 

With the Jetta, I don't know what property of the grease had changed to
become insulating after working OK for a week or so, and it might not have
the same formulation as the same sort of product in the USA.  The greased
connector initially worked OK, but only for a week or so.

Dave.
UK VW Type 3&4 Club
===================

-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Jim Adney
Sent: 28 January 2012 15:45
To: type3 at vwtype3.org
Subject: Re: [T3] Non-Working Headlight

On 28 Jan 2012 at 13:41, Dave Hall wrote:

> I used copper grease on a Jetta starter wire that had become corroded.  
> I cleaned the wire and terminal, and put on a thin coating of copper
grease.
> Worked fine for a week, then simply wouldn't pass the current.  When I 
> cleaned it off again and reassembled without the copper grease it 
> worked fine again, and continued to do so.  I've never trusted copper 
> brease for electrical connections since - you'd think it would be 
> better than normal grease, not worse!

A sample of one may not actually prove anything. It could have been a fluke,
which was cleared by the second loosening/tightening. OTOH, it's possible
that one of the additives in the copper grease reacts with steel to make a
layer which is helpful in reducing friction and wear but also just happens
to be an insulator.

I just use very common normal grease that I assume to have decent rust
inhibitors.

> I also used a smear on spark plug threads for some years, but often 
> got some misfiring after, and didn't connect the two.  I use a drop of 
> oil on the threads instead, and don't get problems any more.

When you put something on SP threads, some will inevitably get onto the head
threads and the leadin to those threads. The next time you install SPs,
there's always a chance of touching the SP insulator to that bit of grease,
leaving a deposit of something conductive on the insulator, which is a bad
thing and can lead to mis-firing. For this reason, Graphite grease is not
recommended for SP threads, and I assume the same thing applies to copper
grease. Oil is fine, and I've 
always used Moly compound on SP threads, with excellent results.   

You don't need to worry about conductivity at the SP threads. There's WAY
more voltage available there to break across any kind of insulating layer
you could imagine.

The important thing is to NEVER install SP threads dry. That can lead to
seizing, which will leave the threads in the head ruined.

--
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************

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