[VAC] Re: 7 Pin Wiring Electrical Connector

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

On my '68 Caravel almost nothing but brake and turn signal lights worked
because of bad grounds on the marker lights. After 400 miles of pulling
two marker lights worked. I rebuilt the marker light grounding last year
and now they all work.

A circuit tester will light on a much smaller current than the lights
and prevent the lights getting enough current to light. To make that
test valid you need a much larger lamp for the circuit tester or to make
the test (battery negative to frame) without a limiter. When using a
battery as a test source, it would be prudent to install a 10 or 15 amp
fuse next to the battery. So if you contact a short you will blow the
fuse instead of putting hundreds of amps into the wires which could burn
them open or at least burn the insulation off (including the insulation
on the wires in your hand).

In my Caravel, there's a junction box accessible from underneath in the
right front corner, that's for the signal and battery circuits. It would
seem likely that the ground wire should be connected there. Some trailer
wiring schemes have depended on the hitch ball for the ground return.
They are easily detected by the flickering marker lights. If the white
wire isn't visible grounded near there, I'd run a wire to the frame and
the shell right there to make that a sure connection. Then go on in the
circuit tracing.

It is entirely possible that every light socket on the trailer system of
trailer (e.g. marker and signal lamps) has a bad ground. My Caravel was
in that shape.

Gerald J.