[s-cars] High beams stay on after relaying

[Fred Munro]

Hi Vincent;

I've attached a post I put together several years ago on this topic. It
applies to Canadian cars with the Daytime Running Lights. I did the "cheap
Fix" I mention in the post - haven't done the "proper Fix" yet (hey, the
cheap fix works great!)

Fred Munro
'94 S4

___ATTACHMENT____

    I've gone through the Bentley wiring diagram, tested the system on my S4
and think I've found the problem causing the high beam relays to latch on.
I've come up with a couple of fixes, but haven't field tested them yet -
thought I'd throw this out to the list for info and comment.

PROBLEM:
    When the stock high beam wiring is used to drive a pair of relays for
Eurolights on the UrS4, the relays will activate when high beam is first
selected and will remain on when low beam is selected. The relays will open
if the headlights are switched off, the fog light relay is removed, or the
stock wiring is removed from one relay and reconnected to one high beam
bulb.

CAUSE:
    The AE (Audi Engineers) have decreed that the fog lights will shut off
when high beams are selected. This is probably due to some obscure safety
legislation or concern about heat in the headlamp housing with 3 bulbs
illuminated. Since the S4 low beams are always on, even when high beams are
selected, the standard dimmer switch cannot be used to trip out J5, the fog
light relay . AE have come up with a rather elegant solution - the coil on
J5 (terminal 85) is grounded through the high beam bulbs. When the high
beams are switched on, terminal 85 gets 12 volts, the same as terminal 86 on
the other side of the coil, and the relay drops out, shutting off the fog
lights. Terminal 86 is only fed power when the headlight switch is fully on.
    Along comes a FAE (Feckless Audi Enthusiast) who installs a set of
Eurolights and relays the high beams to the alternator to get maximum
voltage, maximum lumens, and avoid frying the headlight switches with the
500w "off-road" bulbs he's installed. The stock high beam wiring is used to
trigger the relay coils in time honoured fashion. When the headlights are
turned on with low beam selected, all is well - the fogs work and the low
beams work. High beam is selected, and the relays activate, turning on the
high beams and temporarily blinding the FAE with reflection off the garage
walls. Low beam is selected but the high beams stay on. Once the FAE becomes
aware this is not an image burned into his retinas, he finds it is because
the relay J5 coil is now grounded through the high beam relay coils and is
passing enough current to keep the high beam relays closed. Pulling the J5
relay or shutting off the headlights interrupts the power flow and lets the
high beam relays open. Reconnecting the stock high beam wiring to one bulb
grounds J5 through the lower resistance of the bulb and allows one high beam
relay to work properly.


FIX(es):

    I've come up with two fixes, one which retains the current system
functionality and a cheaper, easier one which doesn't.
    The "Cheap Fix" is to remove the female terminal 85 from the relay J5
socket and insulate it with a piece of shrink tubing. Install another female
terminal into the socket and run it to ground. This will give you fog lights
whenever the headlight switch is "on", even when high beam is selected. You,
the aware and in-control Audi driver, will have to remember to turn them off
when you flip on the highs. Since high beams are not too useful in fog, this
may not be a great hardship.
	The "Proper Fix" is to take the wire mentioned above and rather than run it
to ground, run it to terminal 87 on one of the high beam relays. This will
bypass the relay and ground the Fog Light relay through the high beam bulb
filament, restoring the original system functionality.

-----Original Message-----
From: s-car-list-admin at audifans.com
[mailto:s-car-list-admin at audifans.com]On Behalf Of Vincent Fregeac
Sent: February 23, 2003 10:51 PM
To: s-car-list at audifans.com
Subject: [s-cars] High beams stay on after relaying


Hi all,

Today was headlights day for my urS6: lens cleaning, 9005 for low beams
(not installed yet, I have trouble removing the two pegs in the plug)
and relays. Everything goes well and the improvement is really worth the
trouble but I still have a little glitch. The high beams stay on. I can
switch them off by switching off the headlights but they won't turn off
just with the high beam/low beam switch. I've seen this issue mentioned
in the Euro Supernova article from Igor on www.urs4.com but there is no
fix in the article. Usually, this is due to a current leak and can be
solved by a resistance charge in parallel with the relay coil but I
though I'd rather ask the list before adding something else in the
already crowded passenger headlight enclosure.

BTW, I've not deleted the light check yet. Can it be related?



Vincent.

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.449 / Virus Database: 251 - Release Date: 27/01/2003


_______________________________________________
S-CAR-List mailing list
S-CAR-List at audifans.com
http://www.audifans.com/mailman/listinfo/s-car-list