[T3] Wiring Harness Thoughts

[Jim Adney]

Jeff, I think it's unlikely that replacing your harness would fix your problems. 
Many of the ills that are blamed on "old copper" just don't make sense, and 
even your experience with the nasty residue is not all going to be cured with 
a new harness.

Fire damage is a separate issue. You may be able to replace individual 
wires, but that is often quite difficult. Otherwise, Dennis's suggestion is the 
best one: Find a better, genuine VW harness from a donor '67, because the 
aftermarket harnesses tend to be correct for just a few years, while VW 
made changes almost every year, and sometimes more than once in a year. 
(There were three different versions in '71!) Things were simpler in the early 
years before FI, so that might make your search easier.

Part of your problem may be due to bad grounds. That is certainly the case 
with the gauge lights. VW started adding ground wires to everything in '69, 
which fixed a lot of those problems, but in '67 the instrument lights all 
depend on the retaining clips for their grounds. As time has shrunk the vinyl 
dashpad, those clips no longer get pressed as tightly against the backside of 
the metal dash, making the grounds undependable.

You might also check the retaining springs on each gauge. The mounting 
arms for them often get bent. The 2 arms should be parallel. When mounted 
in the dash, the springs should NOT go outside the little bumps in the metal 
dash. You can feel these bumps if you take one of the gauges out.

Finally, at least starting in '68, there is a ground lug on the brace under the 
glove box that a lot of things used, but this depended on a number of 
daisy-chained wires, that connected a lot of things together. I don't know if 
this was there in '67, but if it was, then it's important for that ground chain to 
be unbroken.

On 22 Mar 2020 at 20:55, Jeff C wrote:

> Many years ago the wiring under my dash started to burn, so I put it
> out using a dry chemical fire extinguisher. Thar stuff is nasty and
> corrodes bare metal. Over time I have been trying to clean connectors
> and such at every opportunity. The turn signals sometimes work,
> sometimes don't. I installed the rebuilt speedometer a couple of weeks
> ago (Thanks Jim) and afterwards, some lights work, some don't. I tested
> the connections at the fuse block and I could get some lights to work
> by removing and re-connecting the wire ends, but not all. This leads me
> to believe that the residual corrosive dry chemical powder is still
> having an affect on the connections. So, I have been fighting the
> wiring for a long time and consistently losing. I was going to go for a
> ride a couple of days ago, but wasn't sure that the lights were
> properly working. Is it time for a full harness replacement? They are
> available, expensive, but I just can't depend on all of the electrics
> to stay working. I replaced a couple of harnesses on my old non-VW
> truck and it has made it consistently reliable. For those who have
> replaced one, please share your experiences. Jeff '67 Squareback 


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