rcarriere wrote:
>
> So can some one describe the procedure for
> tracing this problem to its source, the tools I will need and so on.

I can't remember whether the '56 Chevy had separate bulbs for the brake
lights and running lights, but I will write this as if it did. If it has
one bulb for both, you will have two "center electrodes" in each socket,
and you'll have to figure out which is for the running lights. I also no
longer have a wiring diagram for this car, but most makers ran the wiring
down the left side of the car, so power went to the left running light
before going to the right one. I would start at the left side because I
would bet the problem is either at that junction or further forward in the
car.

Go down to your local parts store and buy the type of electrical tester
that lights up and has a sharp point on one end and a grounding wire with
an alligator clip on the other end. With that car, you want the standard
12V unit. Also buy a new taillight bulb, just to make sure you have one
that works. Remove the left taillight bulb. Check the center electrode in
the socket. This should have a spring under it, and you should be able to
push it down into the socket about 1/8" and have it spring back. If it does
not do this, it may not be contacting the base of the bulb. Turn on the parking
lights and insert your new bulb. If this lights when you push it in hard but
goes out when you relax pressure, the center electrode or its spring is worn
out. Replace the socket.

If the bulb doesn't light, hook the alligator clip of your tester to a good
ground and touch the tip of the tester to the center electrode deep within
the socket. Make sure that you have a good ground; if necessary, run a long
wire back to the battery. When you insert the probe, do NOT let the probe
touch the sides of the socket; the sides are supposed to be ground.

If the tester lights up, you have power at the electrode. Disconnect the clip
from ground and hook it to the side of the light socket and retest. If the
tester does not light up, the ground to the socket is bad. You may have to
replace the socket. If it *does* light up, inspect the entire socket carefully
and try to figure out why it will light up your tester and not light up your
new bulb. The most common reason that I've seen for this is that the electrode
is worn.

Since both lights are out, I expect that you will not have power at the socket.
Trace the wires from the back of the socket to the next upstream (closer to the
battery) connection. With the parking lights on, unplug this connection. If
it's hard to unplug, use WD-40 to loosen it up. Use your tester to check for
power in the upstream part of the connector. Keep going upstream until you
find a connection with power. When you do, clean up all the contacts there
and plug it back together. Then check for power back downtsream. In this way
you will locate the defective connector or wiring section. NAPA sells these
old connectors, if you need one.

If you get all the way back to the headlight switch and find no power, the
problem is your switch.

You can, of course, start at the switch and run the other direction.

One last thing. If you turn the parking lights on and the taillights work
but they don't work with the headlights on, the probelm is almost certainly
the headlight switch.

George Patterson
The optimist feels that we live in the best of all possible worlds. The
pessimist is afraid that he's correct.
James Branch Cavel