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RE: Euro lights w/ Autocheck
Steve and Matt,
>The autocheck headlight test function measures current difference between
>the left and right headlight wires from where it is located.
If you want to keep the Auto-Check headlamp bulb filament monitoring
system, just remove the Lamp Control Unit "Front" (sometimes referred to
the Lamp control relay, it ain't no relay) which is under the driver side
dash area on the auxiliary relay panel.
Install 2 jumpers across the original Lamp Control Unit connector pins (56L
and 56L1, 56R and 56R1), and then mount the Lamp Control Unit somewhere
between the new relays and the Euro lamps.
Connect the relay outputs to terminals 56L and 56R, and run the output from
the Lamp Control Unit (56L1 and 56R1) to the euro lamp low beams. The last
thing to do, is to run the one wire from terminal K on the Lamp Control
Unit back inside the dash area to the terminal 9 on the original Lamp
Control Unit connector block. Not very difficult to do, just a little extra
wiring. Keep in mind that you will drop some voltage through the Lamp
You could also mount your new relays under the dash area and connect
directly to the Lamp Control Unit connector block, and then run the heavier
gauge wires out from the relays to the Euro lamps after passing through the
Lamp Control Unit.
The Lamp Control Unit only has 6 wires connected to it. One for ground, 2
for Left side lamp (1 in, 1 out), 2 for the right side lamp (1 in, 1 out)
and the one wire that goes to the Auto-Check dash connection (Terminal 9/K).
There isn't much inside these "Lamp Control Units", if I remember
correctly, looks like some resistive traces to measure the current out to
the headlamps via a voltage drop, a comparator IC, some diodes and some
resistors. When I bypassed my Auto-Check function, I just pulled up one leg
on a diode inside. Bending over the K terminal on the outside works just as
well to defeat it.
The S4 Lamp Control unit isn't so easy to defeat......as they integrated
more function into it for the other rear lights etc.
For me, whenever I lose a low beam bulb, it becomes so obvious, that any
sort of "warning" is redundant IMHO. Of course there are those drivers you
see out there running around at night with their headlamps off, or with one
side burned out.
>Keep in mind that it is not mandatory that you install relays with the Euro
>lights ... AAMOF as long as you stick to stock wattages you shouldn't have
>to worry about overloading the headlight switch.
Well, I was using the stock wattage bulbs in the stock headlamps in my 89
200TQ, and my low beam terminal burned up on the headlamp switch/connector.
One minute I had low beam headlamps, the other minute nothing. This was one
"feature" I did not appreciate in my Audi.
The low beam terminal pin on the headlamp switch is a smaller diameter than
what is used for the high beam terminal so it gets hot and eventually we
have meltdown. The other problem is the stock wiring which routes the
current through the headlamp switch, and then back out to the headlamps,
drops about 1 volt at the headlamps, so you end up with only about 12.5
volts, far short of the ideal 100% voltage (13.5v) as indicated by the
Hella folks. I have found that even the lousy stock 5000/200T/Q headlamps
work better, just by installing relays with the stock wattage bulbs. Of
course, they still suck big time, and can't hold a candle to the Euro lights.