[VAC] Re: 7 Pin Wiring Electrical Connector

[Dr. Gerald N. Johnson, electrical engineer]

The marker lights mounting is a bad design. Squeezing plastic means the
plastic (check the definition of plastic) gives way under pressure. Then
without a strong spring to maintain the contact pressure, it 
disappears. That was uniformly true of my marker lights. I machined away
the supporting plastic boss under the ground strap, then inserted an
aluminum screw from the inside of the wall of the trailer (either by
working through the large hole under some marker lights or by making a
keyhole to the original rivet hole). I used a stainless steel shake
proof lock washer on the bolt head and coated them with aluminum
conductor connection grease (which is filed with zinc crystals to
puncture aluminum oxide). I then put a pair of nuts on the outside. The
first one to secure the bolt to the skin, and the second to fit under
the ground contact strap in the marker light that I had exposed by
machining the plastic boss away. I put the marker back in place (with a
wad of plumber's putty to fill the hole and slots) with another
stainless steel shake proof lock washer coated with the aluminum
connector grease, and then another aluminum nut. That made the marker
lights bright enough to see with full July sun. I also cleaned the
socket connections with scotchbrite as well as the lamps and coated all
of those with silicone dielectric grease for protection from corrosion.
With an all metal ground path with no plastic to give way, I expect
these marker lights to work for a while. I need to put a little vulkem
around the base of each marker light for further waterproofing. I used a
stainless steel self tapping sheet metal screw in place of the second
rivet on the marker mounting. That way I can tighten it up with a
screwdriver which is far easier than drilling out the rivet and
replacing it.

It was a pain to go to the details I used, but I don't expect to have to
do them again, ever.

The frame is weakened the least if you drill in the middle of the
vertical web.

All my marker lights had the same ground problem, it wasn't one bad
light ground that killed them all, it was that ALL were bad. The white
wire not getting to the frame is a separate problem.

The red wire leaving the post may be for going to the break away switch.
I don't know any other purpose.

One time, while my uncle was working on my bent VW, a customer came in
to his car shop with a pickup where the wrong turn signals would light
on the back. Being an electrical engineer, I dug in (to keep uncle
working on my VW and to help pay for his work). I found that the pickup
bed was no longer grounded to the frame or the cab. When I added ground
wires from the bed to the frame and the cab, then the turn signals
worked right again.

My first full time employer out of college was Collins Radio in Cedar
Rapids. Engineering standards there would not allow using any plastic
(not even HARD plastic) to apply pressure to an electrical connection.
So they would not allow using the mounting bolt of a cinch-jones barrier
strip made of very hard phenolic to ground a wire. The ground stud had
to be separate from the mounting bolt. The plastic based marker lights
failed to meet that standard. I see the current production plastic based
marker lights still have the plastic in the support bosses, but have
grounds on both mounting holes. There is an alternative, probably twice
the price per marker (and not the same shape as those on my Caravel),
that's marker lights from Grote with diecast metal bases. I paid under
$6 for one to have as a sample. 

Use shake proof (sometimes called star) lock washers and aluminum
conductor connection grease for all connections for better longevity.
The stainless steel shake proof lock washers are uncommon in local
hardware stores. I bought metric (100 to the box) in a size that fit my
#10 aluminum screws from McMaster-Carr (www.mcmaster.com). They do sell
#10 but the minimum box was much larger (1000).

Gerald J.



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