Fuse problems

["Mike Nakamura" <mike_nakamura@domain.elided>]

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.  

 

I am not up to speed on technical requirements of a fuse, however at 30
percent over rated capacity, perhaps 60 seconds is normal.  

 

This is an interesting site on wiring headlights.
http://lighting.mbz.org/tech/how_to/relays/

 

Disclosure: I have bought the relay and connector kit from Dan Stern
lighting, I thought it was great.  Otherwise I have no financial
interest in any of the sites noted above.  I don't have direct financial
interest in your car, but if it's an ALFA, I'd like to help keep it from
burning up.

 

Take care.

 

Mike Nakamura

Fall City WA USA

mike_nakamura@domain.elided

91 Spider Veloce

94 164 LS

02 Dakota
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