Re: Headlight relays and fuses

[GLewis4457@domain.elided]

In a message dated 8/6/2002 1:04:17 PM Central Daylight Time, 
owner-alfa-digest@domain.elided writes:

> From: "Mike Nakamura" <mike_nakamura@domain.elided>
> Subject: Fuse problems
> 
> Hi Tony:
> 
> 
> 
> If your car has a front located battery, the 12 gauge wire to the relays
> and lights should be adequate.  I did this project in a Montreal and
> used 12 gauge (tapped the alternator with fuses inches from tap).  The
> object of using large wire is to minimize the voltage drop to the
> headlights.   Your fuse should be as close to the positive tap as
> possible to reduce the possibility of catastrophic fire.  
> 
> 
> 
> Did you run your ground to the battery, engine block or alternator
> bracket?  Since you did all of this work, I assume you supplemented or
> eliminated chassis grounding.
> 
> 
> 
> DC current has less resistance than AC current in the same wire, however
> the low voltage of automotive systems make them more sensitive to
> voltage drops caused by small wire. I hope you ran the 12 gauge to the
> actual headlight connectors and did not splice the 12 gauge to a small
> wire just outside the headlight bucket.  
> 
> 
> 
> Did you use ceramic headlight plugs for the 100w bulbs?  For 100w,
> phenolic connectors are probably okay.  Plastic will melt.
> 
> 
> 
> As noted by other posters, since you're running all 4 hi beam lamps (350
> watts) through one circuit, the 20 amp fuse is too small.  For more
> details on watts, volts, amps, see these two sites.
> http://www.howstuffworks.com/question501.htm     and
> http://www.tpub.com/basae/8.htm
> 
> 
> 
> If 12v, drawing 29.2 amps, 60 seconds sounds is too long for the 20 amp
> fuse to blow.  At 13.5 volts ("normal" running system), 26 amps, 60
> seconds seems more reasonable.  Something else is missing from the
> puzzle.  Maybe the bulbs don't quite draw the full 350 watts.  If you
> test the fuse immediately after starting, perhaps the regulator is
> allowing up to 14-14.5 volts.  
> 
> 
The very fact that Alfa has a seperate fuse for each left/right high/low lamp 
should tell you something.  When I put in relays for my high/low beam 
headlamps and H1 100w driving lights on my 83 GTV6 I put in a seperate relay 
and fuse for each pair.  I used a relay that has two outputs, one each for a 
pair of headlamps.

Jerry in Houston
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