Headlight Wiring Harness, is this good enough?

[Larry C Leung]

Matt,

DC requirements are generally higher than AC, due to the cyclical
nature of AC power vs DC. Also, house wiring
is generally solid core rather than stranded (allowable since houses
don't flex as much) which is more efficient. However, I found the info
on what gauge wire to use from several different websites, which took
into account the temp rating (and existance of conduit) of the
insulation.
I have not, as of this time, taken the time to read the voltage drop at 
the headlights, however, so if you're willing to wait I'll check over the

next several days. 

In terms of extra relays, etc, it also depends upon the access to the 
back of each individual lamp. In the case of the type 44 turbo lamps,
there is only one power connector to the "ground" lead, one for each
+12V lead and one for the city lamp. So, extra relays w/rt to the high 
beam won't help. In the case of the original lister's type 85 model 80
lamps, this isn't an issue, as there is only one high and one low beam
filament. As for relays, there are obviously a relay for each beam, high 
and low. I run two complete harnesses for each side, so the total IS 
4 relays, BTW, and this also controls the current load effectively
increasing
current carrying capacity. 

LL - NY


On Sun, 14 Nov 2004 18:23:29 -0600 "Matt Evans" <matt at mattevans.org>
writes:
> For A/C wiring, 14ga is the NEC standard for short-medium runs of 15A 
> or
> less.  Most recent construction has it.
> 
> Extra new stuff is often using 12ga, as it is required for 20A.  
> When
> re-wiring my houses I've put in 12GA for standard feeder circuits.  
> It's
> harder to work with but the extra capacity is nice.
> 
> I think if I were going to all the effort to custom route and 
> install new
> wires in a car, I'd try 10GA for headlights.  It's going to be a 
> pain no
> matter how big the conductors are.  Might as well put in enough 
> metal to
> know you can handle any load you decide to put on there.  I don't 
> know the
> conductor requirements for DC loads, and I don't remember how 
> stranded vs.
> solid comes into play, but I'd probably go one size bigger than what 
> you
> think you need.  
> 
> One other comment - there is extra cost and complexity in running 
> more
> relays and fuses, but otoh, it is uh.. Non optimal if losing a 
> single fuse
> or single relay means you lose BOTH headlights.  The cats-meow setup 
> is
> separate fuses and relays for each primary bulb (i.e. 4 relays and 4 
> inline
> fuses to cover drivers low, drivers high, pass low, pass high).  
> Separating
> loads out like would let you get away with running more but smaller
> conductors.  
> 
>  
> 
> > -----Original Message-----
> > From: quattro-bounces at audifans.com 
> > [mailto:quattro-bounces at audifans.com] On Behalf Of Larry C Leung
> > Sent: Sunday, November 14, 2004 10:37 AM
> > To: quattro at audifans.com
> > Subject: Re: Headlight Wiring Harness, is this good enough?
> > 
> > 200W/12V  ~ 17 Amps.
> > 
> > To the best of my knowledge, the SUV harness comes with 30 A
> > relays and fuses. It's the wires that are the limitation 
> > here, the risk
> > is melting insulation, which if they use the same wire as they 
> used
> > on my harness, is rated to 105C. 
> > 
> > If you run things as designed, the standard Heavy Duty harness 
> will
> > be marginal, but acceptable, especially if you run the wires in 
> the
> > conduits
> > (as you should, protects against abrasion). One suggestion to 
> improve
> > the margin if you use this set-up, run your wires carefully, 
> > and cut-off
> > the
> > excess wire + conduit, thus reducing the resistance load. I am 
> running
> > the SUVLighting HD harness on my T44turbo (55/60W+55W high) and 
> have
> > had no problems, but I WON'T run 100W bulbs of any kind in 
> > this system,
> > there just isn't the margin in the wires needed to run these 
> > for extended
> > periods (quick flashes are okay).
> > 
> > If you want to run the hi+lo (360W/12 ~ 30A) run together 
> > mod, you will
> > NEED
> >  the Super Heavy Duty. BTW, this isn't optically, the best idea. 
> The
> > concentration 
> > of low beam light closer to the front of the car will tend to 
> > draw your
> > eye closer 
> > into the car, not what you want to do if you need to run High 
> > Beams. It
> > LOOKS 
> > brighter, but as I said, human nature tends to defeat the 
> > purpose of the
> > high beam, 
> > AND there is no extra light being projected further ahead, 
> > which is the
> > purpose of 
> > the high beam in the first place. 
> > 
> > So, the drawbacks, bad lighting in terms of the human/optical 
> system,
> > extra current draw, and extra heat. The gains: more light to 
> > blind other 
> > people.
> > 
> > LL - NY
> > 
> > 
> > > Date: Sun, 14 Nov 2004 10:17:47 -0500
> > > From: David <duandcc_forums at cox.net>
> > > Subject: Headlight Wiring Harness, is this good enough?
> > > To: <quattro at audifans.com>
> > > Message-ID:
> > >        
> > <20041114151747.BDIP20686.lakermmtao07.cox.net at smtp.east.cox.net>
> > > Content-Type: text/plain; charset=ISO-8859-1
> > > 
> > > I have a 1987 Audi COupe GT with Euro headlights (typ85 80 
> lights). 
> > > Right now I am running with the stock wiring and 60/55w H4 
> bulbs. I 
> > > want to run 100/80 watt bulbs and use a relayed wiring harness 
> to 
> > > lower voltage drop and lessen the chances of melting anyting. 
> So, 
> > > given that I want to run 100/80w H4s, are these pecs good 
> enough?
> > > 
> > > "New & Improved Wire Harness features:
> > > 
> > > * 2 OEM Bosch/Tyco (Potter & Brumfield) 40 amp relays 
> > (single & dual 
> > > 87 outputs)
> > > * Heavy Duty interlocking relay sockets with mounting tab
> > > * Fusible link (slow reacting fuse protection) 12 heavy gauge 
> > > automotive wiring
> > > * Black split loom matches OEM to protect against heat and 
> elements
> > > * Male connector(s) to plug into existing headlight socket
> > > * (2 or 4) new headlight sockets (depending on application)
> > > 
> > > The Heavy Duty models are 14 gauge wire.
> > > 
> > > They also offer a H4 Super Heavy Duty model is 12 gauge and uses 
> 4 
> > > relays. But it's quite a bit more expensive and if I don't need 
> it, 
> > > I will just get the Heavy Duty one...
> > > 
> > > Also, they offer a mod to their harnesses that allow you to keep 
> 
> > > your low beam on when you turn on the high beam. Good idea or 
> bad? 
> > > If I got it and was running the 100/80w bulbs, that wwould be 
> 180w 
> > > combined per bulb. Down sides? Too much heat? Too much current 
> draw?
> > > 
> > > TIA!
> > > 
> > > Dave
> > > 
> > > 1987 Coupe GT Special Build 2.3 
> > > All in SE VA
> > > 
> > _______________________________________________
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> > quattro at audifans.com
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> > 
> 
> 
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