Re: [VAC] Marker light grounding. New idea tested.

["Dr. Gerald N. Johnson" <geraldj@xxxxxxxx>]

As of this evening, I've mounted three old marker lights with my new
mounting. The first one I did about 5:30 PM and it was bright enough to
see with full sun in the middle of Iowa. That's some progress.

I've changed dimensions a little, because I didn't realize what parts I
had...

The ground is made with an aluminum screw 10-24 x 1" round head. I drill
the ground rivet hole to pass that screw. Then I put a bit of aluminum
connection grease on the underside of the screw head, and push a
stainless steel internal star lock washer into the grease. Then I coat
the underside of the lock washer that's going to be against the
Airstream skin. Then where there's a working hole behind the marker
light, I use long nose pliers to work the screw and lock washer into the
hole from the inside (dropped one out of three so far) and put a nut on
the outside of the skin. I tighten that nut securely because that's what
holds the skin part of the ground connection. Then I run another 10-24
nut down on the screw to make the stack match the distance from the
surface to the ground strap in the light. I fish the wire (with female
space lug in my Caravel) through it's hole, fill up the back of the
light with plumber's putty and set it over the ground stud. I'd already
drilled out the plastic spacer so the backside of the ground strap sits
on the second nut on the screw. I anchor the other end of the light with
a #12 x 3/4 stainless steel self tapping screw (just fits the rivet hole
nicely), and apply more aluminum connection grease to the ground strap,
then a stainless steel internal star lock washer and more grease, then
the third 10-24 nut. And I tighten securely. The wire lead came through
a rubber grommet but that has rotted especially on the end of the
trailer that saw the most sun while it sat decades. I filled that space
with more plumber's putty.

While I had the marker lights off for drilling, I cleaned off the old
plumber's putty (still pliable at 32 years), checked all the lamps and
coated the lamp connection points with silicone dielectric grease to
slow their corrosion. I'll have to replace a couple of the 3/16" female
flag spade terminals because they pulled off the wire instead of through
the hole. If they pulled off, they were poorly connected anyway. I'll
use straight ones to replace them.

Most, but not all of my marker lights have a 1-1/4" or so hole behind
them for wiring access. Those that don't I'll probably drill a 3/8" hole
about a half inch from the grounding rivet hole and then make a slot so
the screw can go in like a keyhole slot. A wad of plumber's putty or
Vulkem will close it off and it will be hidden by the marker light.

Just in case, I've ordered a spare Grote model 46792 die case marker
light to see if I find its construction enough superior to abandon this
scheme and to replace all the marker lights. The cost is projected to be
$5.63 per marker light, with lamps.

This seems to be a lot of trouble, but with the bad grounds that I found
universal to my collection of marker lights, there was no good way of
making a fix on the road. I figure that making the ground connection
higher quality and not dependent on the compression of plastic will make
them function far longer. At the worst, it will take a 5/16" nut driver
and #3 phillips screwdriver to remove and clean and reassemble in the
future. Far easier than tightening pop rivets.

I'll think about making and posting a sketch of the process on my
Caravel web page. But not tonight. Would have been nice to borrow a
digital camera, but the handy one is on its way to Alaska this week.

Gerald J.