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More Voltage, Igor, More Voltage!
- To: firstname.lastname@example.org
- Subject: More Voltage, Igor, More Voltage!
- From: email@example.com (Robert D. Houk)
- Date: Wed, 17 Aug 94 15:32:50 EDT
- Reply-To: quattro
- Sender: quattro-owner
Having just (more or less) finished a substantial wire revamping in
my UrQ, I thought I'd share the results with ya.
Symptom: Headlights only get 9.63 volts.
Diagnosis: Audi wiring sucks.
Cure: Do it myself.
Ya gotta laugh when you see a 10ga wire feeding the "ignition on" power
bus through a 16ga intermediate wire from the key switch to the main
fuse panel, back out via a 12 ga to the fuel pump and back in to the
main fuse panel to a 25A fuse to the radiator fan circuit . . .
As it turns out, the main fuse panel had already fused itself once, and
been replaced by a previous moron, so the wiring was something of a mess.
While tempted to blame the inadequate wiring on the previous owner rather
than upon the World's Most Competent Engineers(tm), I will point out that
the rewiring was not melting...just kinda messy and incompetent. As an
example of what makes the task so much fun, the "A" plug that feeds the
main fuse panel was wired "upside down", but, being symmetrical, the idiot
simply filed off the "key" tabs so that the connector would fit in upside
down... Sigh. Fortunately, the wire tends to take a "set" so it is easy
to remember which way is electrically-correct.
Anyways, step one was to run a dedicated 10ga from the battery to the
#30 terminal (that's apparently GermanSpeak for "unswitched +12V terminal",
there's gotta be some interesting folklore behind this nomenclature!) of
the ignition switch, bypassing the main fuse panel completely. This step
alone won me somethink like 3V at the headlights (low beam), and was
the single biggest win. It also won nearly a volt at the switched +12V
power bus (I believe proper GermanSpeak is the #15 terminal) of the fuse
panel, so the engine computer got an extra volt out of the deal; the car
idles better too! [I'm told the UrQ's engine computer is notoriously sen-
sitive to low voltage...I believe it too!]
Step two was to run a dedicated 10ga from the battery to the radiator
fan fuse input terminal on the back of the main fuse panel (thus off-
loading the 16ga feeder wire...). As part of this, step two-A was to
reroute the A/C circuit to switch the radiator high-speed-fan-relay
rather than the radiator high-speed-fan directly. This had several
desireable effects, most notable of which was nearly an extra volt to
the radiator fan...(bypassing about 8 electrical feet of wire and
several relays and intervening fuse). It also now means the radiator
fan always runs through the radiator fan fuse, and not sometimes
through the fresh-air fan fuse! (Which, by the by, is not only *NOT*
in the main fuse panel as indicated by the fuse label, and *NOT* even
in the auxiliarly fuse panel as indicated by the special factory an-
ciliary manual, but is a separate tertiary fuse panel sitting above
the glove box, feeding the three A/C relays...Woof!)
Step three was to run a dedicated 10ga from the battery to the headlight
switch (bypassing/offloading the ignition switch). Actually, I ran the
10ga to behind the fuse panel where I split it into several 12ga feeds,
one of which is the headlight switch. This, by itself, didn't seem to
win much, maybe .1V at most -- 12.3V at the headlights (low beam). Some
careful measurments at this point showed loses of 44mv across the head-
light switch itself, and 130mv across the [right] lowbeam fuse (and 180mv
across the left). I also noted 260mv from the headlight ground terminal
to ground! High beams were still suffering significantly however, at only
10.56V, so the "dimmer" switch appeared to be a significant resistance.
Step four was to install a relay to switch the highbeams. I got cute
and did all this from inside the car, on the main fuse/relay panel. Since
there were some unused relay sockets, I snarfed the left-most one (which
has something to do with an optional oil pressure controller (or somesuch
gobbledygook; it's not real clear from the Bently...or the Audi docs).
The contacts/socket disassemble fairly easily, so I heat-shrink-tubing'ed
all the exposed contacts, and tie-wrapped them out of the way (I couldn't
quite bring myself to actually *CUT* the wires out to help clean up the
rat's nest), then ran a pair of 12ga feeders from the aformentioned 10ga
#30 lights wire to the recycled relay socket to feed the left and right
highbeams -- I cut the wires (one from "A" connector, one from "C" connec-
tor behind fuse panel), spliced in a "Littlefuse" inline fuseholder for
each circuit, then ran the "C" connector highbeam wire to control the
DPST relay itself. This got me 12.8V at the highbeams (still running some
260mv from headlight ground connection to engine/body ground though;
measured 30mv across one set of relay contacts and 76mv across the other).
WORLD OF DIFFERENCE! The lights actually light up the night now! And it
all looks "factory" (until you actually pull the wires and notice the
Littlefuse fuseholders...those sucky ceramic krock fuses are real junk...
and they run HOT too! Burned myself on one -- lowbeam -- in the process
of tracing/experimenting with all this stuff). Boy are Audi relays ex-
pen$ive little suckers! But dual 25A relay contacts feeding 20A fuses
give me room for, um, growth in the lights arena. And there's that spare
slot in the instrument console for the fog/driving light switch (although
I shudder to think what Audi is gonna extort from me for that switch),
and there even just happens to be a spare 12ga feeder wire hanging out
in the region of that open switch slot (What a Coincidence!).
I also soldered all connectors after crimping the wires... (as far as I
am concerned, crimping is for mechanical hold only, soldering finishes
the job!). Hint -- remember to put the heat-shrink tubing on the wire
*BEFORE* you make any butt-splice connections. I know it sounds really
obvious, but . . . but in the passion of the moment it's real easy to
overlook the obvious, and it's *REALLY* annoying to have to cut a wire
an inch down from a nice new but splice to slip on a piece of heat-shrink!
I kinda pseudo-paranoically-cheated on the battery connections: I ran an
8ga wire from battery to a Littlefuse Maxifuse fuse block ["Littlefuse
is a company trade name; "Maxifuse" is particular product name, Maxifuses
are like the new dual-spade plastic-encased fuses on steroids, the spade
connectors make really good contacts: only 20mv drop across the fuse]
which I used to feed a pair of 10ga wires -- I *really* wanted some kind
of fuse in the circuit somewhere, and these fit nicely under the seat
right beside the battery. I put in two of these guys [the fourth 10ga is
for the rear amps, soon as I get around to finishing the project...]. I
feel confident that any sort of collision/accident that shorts a 10ga
wire will blow even a 50amp Maxifuse RIGHT NOW, so I am safe. Everything
else is independently fused (I maintained separate left/right headlight
fuses...) to protect the individual circuit/components. As much as they
are a hassle, I am a strong proponet of fuses for safety purposes (a 12V
lead/acid car battery will easily vaporize heavy cable, screwdrivers,
'Course now I have to carry an assortment of ceramic fuses, glass fuses,
AND maxifuses...Sigh. But I have headlights (Hella Q/H, of course, of the
55/60wt persuasion, plus 60wt high beams; 100wt'ers will be a future ex-
periment) that WORK, and the engine idles better too!