Last update: 6/30/08 |
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Background Normally a Locost's
front turn signals are partially blocked for viewing from the sides by
the
bezel hardware. I mounted a pair of 1995(?) Nissan amber sidelights
just in front of
the foot wells on either side of the car. In studying an old American
car wiring harness I found out how the manufacturer wired the front
sidelights to also act as turn signal indicators.
Caution
How to wire the light Wire one lead of the
sidelight bulb to the "hot"
parking light lead and the other lead from the sidelight is connected
to either the left or right turn signal "hot" lead depending on which
side of the car you are wiring at the time. That's
it!
Theory The left and right
turn
signal circuits use hi wattage bulbs to give a
bright turn signal illumination. Normal "parking" lights
use bulbs
that are generally 4 watts or more each so they can't be wired as turn
signals using this method. The [normally amber]
sidelights use a rather small wattage bulb in
comparison to the turn signal bulbs on the circuit. By wiring the #194
sidelight bulb as described above, the sidelight bulb can be
illuminated by
the active circuit (either turn or parking light) and uses
the turn signal circuit to "ground" the #194 bulb through the
unlit turn signal circuitry.
Examples Lets assume you turn
the parking lights ON and at that time
both the left and right turn signals are OFF. The sidelights see 12
volts on one lead of each bulb. At the same time the -other- lead of
each sidelight is connected to their respective turn signal circuits
that are not energized. The bulbs of the turn signals present a low
resistance path to ground. This causes the current through sidelight
bulb
to illuminate through
the turn signal bulb grounds. The turn signal bulbs don't light because
the
sidelight bulb can't pass enough current to allow them to light but the
turn signals can pass enough current for the sidelight bulbs to light.
Now let's assume you have the parking lights ON and you now turn ON your right turn signal. When the right turn signal circuit has 12 volts on it to flash the turn signal bulbs the right sidelight will have 12 volts on BOTH leads. This will cause the right sidelight to flash OFF because there is no voltage drop possible across the bulb. The left sidelight is unaffected by the right side flasher and stays ON. The same action applies when the left turn signal is used. Now let's assume you have the parking lights OFF, and you turn ON one of the turn signals. When the turn signal circuit has 12 volts on it to flash the signal the same 12 volts will be on one of the sidelight wires and the other wire of that sidelight is grounded through the parking light circuitry. The interesting thing about this circuit is that when the parking lights are OFF the sidelights flash in cadence with the turn signals. When the parking lights are ON the sidelights flash ON when the turn signal lamps flash OFF! |
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