[T3] Non-Working Headlight

[Jim Adney]

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.

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