5KTQ Headlight Wiring

[Ameer Antar]

I thought about that too, but the battery, and even the rest of the 12V 
wires in the car should be at 13.8V as well. You get 14.4V w/ no load, but 
as long as the battery [batt. has internal resistance] and the car's load 
is attached, that voltage goes down under that load. The regulator in the 
alt. is a simple diode circuit and does change under load. The only way for 
the batt. to be lower voltage than the alt. is for a large resistance 
between the two. Since there's a 4 or 8 ga wire between them, and not a 
resistance wire, the voltages are about the same. You have to remember that 
the whole car has a poor regulation system. It can go from 11V-14.4V [most 
car amp manuf's spec 11-14V].

With the stock setup and their thin wires, I once measured 10V across my 
high beams. So there was a 2-3V drop from system voltage, but that's b/c 
they used 20 ga. wire. By using thick gage wire and hooking to a direct 
source, you give the bulbs the full power from the car. But even if you ran 
a fat wire from the batt. directly to the new bulb circuits, it'd be the 
same as getting power from the alt, since they are connected w/ a fat wire.

In any case, I think the stock bulbs last longer than they were designed 
to, since they run under lower voltage. But the relay setup gives the full 
voltage, which is part of the performance increase, which may cause the 
bulbs to live shorter than stock lives. But I bet they still meet there 
life expectancy. I bought decent H4 bulbs, and they've been fine now for 
several months.

One thing about using the stock bulb connector is that it's different than 
the H4 setup. If you wire it exactly the same way, you will constantly run 
both high and low beams [that is for 2-filament bulbs]. The difference is 
just switching a ground w/ one of the other wires. They sell H4-to-sealed 
beam adaptors, but there's no need, since you'll be using relays and wiring 
it yourself. You can find lot's of info here: 
http://catalog.com/susq/other/headlamp.htm

an multimeter will help too. good luck.

-ameer

-ameer

At 01:13 PM 11/6/00, Livolsi, Stephane wrote:
>I am not quite positive on the details but this might lead to shorter bulb
>life.  I imagine the headlamps are rated 12V but if you get the power from
>the alternator you will be getting more than that, all the time (isn't it
>13.5 or 14 V output at the alternator?)  I think the underhood battery
>terminal is also unregulated, isn't it?
>
>
>Stephane
> > ----------
> > From:         Ameer Antar[SMTP:ameer at snet.net]
> > Sent:         November 6, 2000 9:16 AM
> > To:   Jack Gagnon
> > Cc:   quattro at audifans.com
> > Subject:      Re: 5ktq Headlight Wiring
> >
> > At 06:28 AM 11/6/00, you wrote:
> > >I just converted my 87 5ktq to the older quad headlight set-up in an
> > attempt
> > >to get decent lighting.
> > >
> > >I temporarily put in some over the shelf Sylvania cool blues that are
> > much
> > >better than the stock aero lights, but I am going to get some Hella H4's
> > >with 50/100 bulbs.
> > >
> > >Does anyone know if I need to install relays and heavier wire for this
> > >combo?  I would assume so.  I think I need new plugs also since the Audi
> > >ones are pretty wimpy.
> >
> > I also upgraded my quad lights, but as long as the wires for the plugs are
> >
> > short, you'll be ok. In truth current capacity doesn't only depend on wire
> >
> > gage, length is just as important. A 20 gage wire can handle maybe 100A if
> >
> > it's a foot long, but after 10ft, it cannot handle much more than a few
> > amps. So keep the plug wires short, and splice them into 16-14 ga. wire to
> >
> > connect to the relays.
> >
> >
> > >I was thinking that I could tap the jump start wire located near the air
> > box
> > >and use the existing headlight wiring to activate the relay.
> > >
> > >Does anyone have a recommended setup for this?  I need to know where to
> > get
> > >the relays, how many are needed, wire size and where to buy the plugs.
> >
> >
> > I actually got power for the lights directly from the alternator w/ an
> > inline fuse. Either way is fine, but it was just easier for me, cuz all I
> > needed was a ring term. to connect to the alt. output post. I used 4
> > relays...one for each bulb. It's not necessary unless you use high power
> > bulbs, b/c the left and right headlights always need to be on at the same
> > time. But if you use 2 bulbs on one relay, it must be able to handle the
> > bulb current *2 which could be ~20A for 2 100W bulbs.
> >
> > I think the key to good lighting is a good lens w/ a decent pattern, and
> > decent bulbs. Hella is a decent choice for both bulb and lens. High
> > wattage
> > bulbs offer more light, but aren't really necessary if you have a good
> > pattern. good luck.
> >
> > -ameer
> >