[VAC] Re: Running Lights

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

On my '69 Caravel only one marker lit occasionally. My problem was
universally the ground connects at each running light. The lights were
mounted with pop rivets providing the ground and pulling against the
plastic base of the fixtures. E.g. depended on plastic in compression.
Since the definition of plastic is that it gives way under pressure,
every last fixture was NOT grounded.

What I did was to remove all fixtures by drilling out the pop rivets. I
found 1-1/4" or larger holes under some of the fixture, and none under
others, just a grometted hole for the wire. The large holes had been
plugged with a wad of plumber's putty. I don't know if this was a
factory patch, dealer patch or prior owner patch. The large holes did
tend to give access to wire nutted wire junctions.

My cure was a bit messy, and I don't know where to find replacements for
the parts I used... I bought #8 stainless steel internal tooth shake
proof lock washers from McMaster-Carr (might have been metric because in
metric I only had to buy 100 instead of 1000). I had an adequate supply
of 8-32 x 1-1/4" or so round head aluminum screws and an almost adequate
supply of matching aluminum nuts that were 5/16" across the flats. I
also already had a supply of aluminum conductor grease used for modern
aluminum wiring connections.

Where there was the large hole, I opened up the rivet hole to pass the
#8 screw. Then with a bit of aluminum connection grease and a shakeproof
lock washer on the screw I used needle nose long reach pliers to insert
the screw from the inside of the trailer out the hole. I immediately ran
on one nut. Then with that nut tightened securely, I ran on another as a
spacer. I took all the fixtures and drilled away the mounting post under
the ground strap with a 3/8" diameter end mill that had a flat tip. I
could have done equally as well with a standard drill bit since the
ground strap flexed away from the milling cutter.

I bought stainless steel self tapping screws to fit the old rivet hole
for the second end of the fixture.

I put the fixture back in place over the aluminum screw sticking out
(probably with a bit of aluminum connection grease again, then mounted
the fixture with the stainless steel self tapping screw after filling
the back or the hole with plumber's putty. Then I added a stainless
steel lock washer coated in aluminum connection grease and a nut to make
the final connection to the ground strap of the fixture.

Where there was no large hole under a fixture, I drilled a hole an inch
to the side (staying under the fixture) of the original grounding rivet
hole large enough to pass the head and lock washer of one of my aluminum
screws. Then I used a 3/16" router bit (but turning slowly in my
electric drill) to cut a slot to the original mounting hole. Made a
keyhole slot as it were in the shell. That was easier to install the
screw as described above. I closed up the slot with a wad of plumber's
putty.

The important thing is that I made the ground independent of squeezing
plastic. That could have been done with self tapping screws and less
shell cutting, probably, by removing the plastic spacer and making one
from aluminum tubing. Still the shakeproof lock washers and aluminum
connection grease is a good idea. The self tapping screw will probably
vibrate loose, but is easily tightened, as is my triple nutted aluminum
screw.

One other technique that should work well, though expensively is to
replace the original Grote plastic based fixture with a die cast base
Grote fixture. Unfortunately the only ones they have with a die cast
base is more square than the '68 Caravel originals and costs at least
twice the cost of the plastic based fixture.

To check for it being the same grounding problem, take a screwdriver and
short from the rivet through the ground strap to the ground strap, or
connect a test light or volt meter to the trailer frame and look for
voltage on the wire and voltage on the fixture ground strap. Mine were
so universally open, I expect all others to be that way. After this
super grounding job, I can see my marker lights in full sun.

I did this procedure to all markers, and was careful to acquire a supply
of lamps. I used only one or two new lamps in 20 sockets. I did polish
lamp sockets and lamp bases with purple Scotch Brite. Then I applied a
bit of clear Ford ignition and lamp base silicone dielectric grease,
part number F8AZ-19G208AA. Likely the dielectric grease sold for
ignition connections at NAPA for 1/4 the price is just as good, but my
'86 Ford had no lamp connection problems at age 14 using the Ford
specified grease from the factory so I paid Ford's price.

I've started to make a drawing of the screw and nut stack, but have not
finished it or converted to something I can post to a web page.

The aluminum screws and nuts, I believe, were sold by Reynold's do it
yourself aluminum line 20 or 25 years ago. I can find screws, I've not
found 8-32 nuts 5/16" across the flats. The standard nuts are 11/32 or
3/8" across the flats and would require a larger hole under the ground
strap on the original Grote fixture. Also the small outside nuts were
thinner and the pair just the right height. Standard sized nuts would be
too tall in the 8-32 dimension. 6-32 might be a better choice if
available in aluminum. They are from McMaster-Carr (www.mcmaster.com).

I used as much aluminum hardware as possible using only stainless steel
for the lock washers and I applied the aluminum connection grease to
minimize corrosion from differing metals in a wet location.

Gerald J.