[s-cars] Headlamp relay wiring weirdness - Insight needed

[Dave Ellis]

Upon further reading I've found a reference to a possible similar 
problem experienced by Fred Munro back in 2000 when relaying a set of 
Euro headlamp assemblies:

"Igor's Supernova Headlight Modification" on S-cars.org:
http://www.s-cars.org/postnuke/modules.php?op=modload&name=News&file=article&sid=77&mode=thread&order=0&thold=0

      "Fred Munro in one of his posts (UrS4 Euro Light
       Hi Beam Relay "Latch-on" Fix of Sat, 8 Jan 2000
       08:38:46 -0500) described the problem associated
       with the Highs not turning OFF in the relayed
       Euro lights."

Unfortunately I've been unable to locate a copy of that post.  If anyone 
has a copy of the thread or a pointer to an archived location I'd much 
appreciate it.

Thanks!
-Dave



Dave Ellis wrote:
> As part of my headlamp rebuild project this winter I installed a new
> wiring harness with relays for the 9011/9012 bulbs on my '93 S4.
> Everything's together now and I was able to test it last night, but I've
> run into some strange behaviour that I'm hoping the group's collective
> wisdom might help sort out.
> 
> When the headlamp control stalk is set to the first or second notch, the
> low beams come on as expected (DRL equipped Canadian model) since the
> lower voltage for the DRLs is enough to trigger the low beam relay and
> bring on the low beams.  But when I move the control stalk to the third
> position which should be low beams on (and for which I expect to see no
> change with relays installed), instead of no change the low beams remain
> on but the high beams also come on.   Usually both highs come on, but
> occasionally only one or the other does, usually when the ignition is
> off.  Weird.  Pushing or pulling the high beam stalk has no further effect.
> 
> At this point I've ruled out any wiring mix-ups, and I have no real
> ideas other than a vague notion it may be some sort of ground loop
> problem.  It appears to have something to do with the higher voltage
> sent for normal low beam operation as opposed to the low voltage
> normally sent to the lows for DRL operation.  The fact that sometimes
> only one high beam comes on when the engine is not running (and so lower
> voltage is supplied from the battery rather than from the alternator as
> would be the case with the engine running) leads me to suspect some sort
> of voltage sensitivity related issue.
> 
> Anyone ever run into this type of issue before?  Any ideas?
> 
> Thanks!
> -Dave