The purpose of a relay system is to reduce the voltage drop that occurs in
the wiring from the battery to the headlight switch, then to the dimmer
switch, and finally from the dimmer switch to the headlight bulbs.
There is another source of voltage drop that can be as much as half of the
problem, which is the resistance of the ground return path, via the third
wire on the bulb socket, which is usually connected to the sheet metal of
the body near the headlight, and thence via various bolts and metal to metal
contacts back to the ground terminal of the battery. Often, one's headlight
can be brightened up considerably by simply replacing all this with a wire
from the third (ground) terminal of each bulb socket directly to the
location at which the battery ground terminal is connected, usually at the
engine block. Of course, each of the connections of this wire must be made
with clean metal contact, using soldered connectors, and the bulb socket
terminals must be clean and bright as well. The wire must be heavy enough
to carry the 15 amp current of the two headlights (12 volt system) or 30 amp
current for a 6 volt system, with minimal voltage drop. This means you need
at least #12 wires for 12 volts, and #10 for a 6 volt system.
The relay cure for dim lights is much more effective on 6 volt cars, since
the currents are doubled for the same wattage bulbs, and the loss of 1/2
volt or so is much more destructive to light intensity. The brightness of a
bulb goes as the 3/2 power of voltage applied, so the loss of 8% of the
voltage (1/2 volt on a 6 volt system) results in a 17% light intensity loss.
With a 12 volt system, usually this is not a serious problem unless the
connections are really in poor condition.
Another strong determinant of headlight brightness is the setting of the
voltage regulator of the car. To keep the lights at design brightness and
to keep the battery fully charged, the regulator should keep the alternator
or generator output voltage around 14.6 volts at normal operating
temperatures (7.3 volts on a 6 volt car) - if this is the case and all the
wiring and switches are in good shape, the light intensity should be
adequate without the "Band-Aid" approach and expense of a relay system.
If you are contemplating installing modern, higher current headlights, be
sure that the circuit breaker and all the switching hardware is up to the
increased current, or you will experience the fun of having your headlights
go out after driving for a while, as the circuit breaker overheats and
cycles off and on to prevent a fire. You're best bet is to increase all the
headlight wiring size by at least one increment over the factory original,
and to change the circuit breaker for an uprated one. Most 12 volt cars
have a mixture of #12 and #14 wire in the headlight system, it should all be
at least #12 if a brighter bulb is to be used.
Dick Benjamin (who doesn't play an EE on television, I are one!)
----- Original Message -----
From: Paul Volkmann <imperial65@xxxxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Monday, January 14, 2002 11:00 AM
Subject: IML: LIGHT up
> A BIG discussion on the C-body list about our old, dim headlights (I only
> read a little of it) about retro-fitting HIDs, HID look-a-likes, where to
> get more power, etc., etc.
>
> Here's my input to the discussion --- (I feel it's useful info here as
well)
>
> Hi guys (and gals)
>
> In the latest issue of Mopar Muscle (March '02) on page 86 (Parts Dept. --
> for you MM readers)
>
> I quote --------
>
> Night Lighters
> Are your headlights as bright as they could be? Jacobs Electronics offers
a
> kit that will brighten your headlights by 42% over the OEM wiring. By
> installing their relay system between the alternator and the headlights,
the
> voltage is increased. They have kits to fit both 2-light and 4-light
> systems.
> Contact Jacobs Electronics, Dept MPRM, 500 N. Baird St., Midland, TX 79701
> or call (800) 627-8800
>
> ------ unquote
>
>
> It seems to me a simple relay system would be better then trying to retro
a
> HID system (or facsimile of one)
>
>
> _________________________________________________________________
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http://explorer.msn.com/intl.asp.
>
>
>
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