Originally Posted by muleguitar

ok, i'll copy and paste this from a thread from 2005. i tried it and it really works. i have been driving the freeways and determined it would be alot safer if my front side-marker lamps would blink as well. here's the mod i performed, and did it without a test light like it explains. just use common sense to determine which color wires do what, and you can do it without having to use extra wire. all i needed was a razor blade, needle nose plyers, and a roll of electrical tape. here it is:

The whole job involves only re-routing one wire on each side. You just
need to check carefully to ensure that you've identified the right ones.

1) Switch on the vehicle's parking lights and 4-way emergency flashers.
You don't need to run the engine during this test unless the battery
is severely low.

2) Using the test light on the wiring going into each turn signal, identify
the wire carrying the blinking turn-signal power.

3) Using the test light on the wiring going into each front side marker
lamp, identify the ground wire (the one that's _not_ hot).

4) Switch the vehicle lights off. You don't need to disconnect the battery.

5) In the next step, you're going to snip the ground wire coming from the
marker lamp and connect that wire to the turn signal's power feed. Work
out the best way to snake the marker lamp ground wire around to a point
where you can tap it into the turn signal's power feed wire, using an
extension of 14-gauge wire if necessary. Pay attention to what cavities
or openings might be filled when you reinstall the light assemblies, if
you removed them previously. You don't want to pinch the rerouted wires.

Note: Don't get confused here. The idea is to run the ground wire
FROM the marker lamp TO the turn signal. Currently it runs
from the marker lamp into the wiring harness and grounds
somewhere. You're _not_ trying to connect the harness ground
to the turn signal!

6) Cut the ground wire coming from the marker lamp, giving yourself as much
wire length as possible from the marker lamp to the cut point. Tape the
cut end of the ground wire that goes into the vehicle harness and stuff
it out of the way.

7) Connect the ground wire leading from the marker lamp to the hot lead
going to the turn signal on that side. Tape or otherwise weatherproof
the connection, and you're done.

Originally Posted by ctubutis

Did you first cut the black wire to disconnect it from ground? And, did you connect
the turn signal power to the black wire going to the LAMP and not to ground?

EDIT: It just occurred to me, don't vans have separate rear side lamps? If so, you
would need to do this mod to both the front and back.

Originally Posted by ctubutis

The pictures are deceiving, the trucks also use two-wire side marker sockets.
The power to the side marker sockets normally comes from the brown wire;
each of those sockets are connected to the same circuit, the same brown wire.
IOW the brown wire begins at the headlight switch and connects to the
left-front side marker socket; it leaves that socket and continues on to socket
on the other side; from there, it needs to go to the rear sockets.

The exact routing is probably not exactly like I described it but the effect is the
same. The same circuit also powers the license plate illumination. Some trucks
also have orange marker lamps on the roof that are connected to that same
brown-wire circuit, and some (all?) have the headlight-on warning buzzer
connected to that same circuit (even if there is no physical buzzer installed, the
wiring is there for one).

The gist of it is, the sockets themselves use single-filament bulbs and are
two-wire sockets; one for power, the other for ground.



I'm not aware of any vehicles that use two-filament bulbs and three-wire
sockets on any side markers. In two-filament bulbs, one is lit continuously and
the other is lit momentarily (e.g. when the brakes are applied or the turn
signals/emergency flashers are activated). The side markers are either on or
off, nothing more.

So, two-filament side markers are all you will need but do this same mod to the
back, too.