[s-cars] FW: UrS4 Euro High Beam Relay "Latch-on" Fix

[Fred Munro]

Hi Bob;

Boy, now you're stretching my memory modules.

OK, first do this test: get the high beams latched on ( high beams on with
low beam selected). Remove the fog light relay J5 from the relay box under
the hood. Did the high beams go off? If they did, my fix will work for you.
If they didn't, I don't have the foggiest idea what your problem is :o).

Attached below is my (updated) original post explaining the cause of the
problem and my proposed fixes.
I'm currently running the "cheap fix" because so far I've been too lazy to
connect the proper fix (which is updated in the attached post).

As mentioned in the diatribe below, the fog light relay coil grounds through
the high beam bulbs. When you relay the high beams, the fog light relay now
grounds through the high beam relay coils because you've naturally used the
high beam wires to drive the new relays. Once you activate the high beam
relays, the fog light relay coil passes enough current to keep the HB relays
closed, even after you switch the high beams off. This depends on the relays
installed - some relays have a higher drop-out voltage and don't cause a
"latching" problem.

So, I solved my problem by removing terminal 85 from the fog light relay and
installing a new terminal and wire (available from the dealer). I insulated
the old terminal and left it in the harness. The new terminal I attached to
a ground. The fog lights now come on whenever the fog light switch is
activated, whether the high beams are on or not.

The proper fix is to connect this new wire to a wire connected to terminal
87 on one of the new high beam relays. This once again grounds the fog light
relay coil through the high beam bulb filament, restoring the fog light
system to it's original function. I've connected this wire to terminal 87
and run it through my left headlight case but haven't got around to
connecting it up to the fog light relay yet.

HTH Bob. The original post is attached below.

Fred Munro


>> Original High Beam Latching Post <<

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.

UPDATED: The "Good and Proper Fix" is to connect a wire to terminal 87 on
the left headlight high beam relay and connect it to a new wire attached to
terminal 85 on the fog light really as described in the "cheap fix". This
again grounds relay J5 through a high beam filament and restores the fog
light system to it's original functionality ( the fogs automatically turn
off when high beams are selected). If this high beam bulb burns out,
however, the fog lights will not work until the bulb is replaced.


I installed the "cheap" fix and it works. I haven't installed the "proper"
fix yet.


Fred Munro
'94 S4  96k km


-----Original Message-----
From: s-car-list-admin at audifans.com
[mailto:s-car-list-admin at audifans.com]On Behalf Of Robert Pacifico
Sent: December 15, 2002 11:34 AM
To: s-car-list at audifans.com
Subject: [s-cars] FW: UrS4 Euro High Beam Relay "Latch-on" Fix




-----Original Message-----
From: Robert Pacifico [mailto:rpacifico at ameritech.net]
Sent: Sunday, December 15, 2002 10:32 AM
To: munrof at sympatico.ca
Cc: S-Car-List
Subject: UrS4 Euro High Beam Relay "Latch-on" Fix


Fred,

Having just completed the above upgrade installation in my 95.5 S6, I have
become the latest recipient of the Munro "Latch-on" Syndrome. The headlights
were sourced from PG Performance and Paul Jr. installed the 40 w relays in
the assemblies. I built the harness per Igor Kessel's post and also noted
his comments concerning your latch-on problem from 8 January 2000. Sooo, I
am MOST curious how you solved the problem. Oh, I did install a modified
AutoChek box from Blau as the last time I did this in my 93 S4 I used Blau's
harness and they included the box. Could this be the problem?

Thanks in advance.

Bob, beaming it up in Crystal Lake, Pacifico

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