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

[Wayne Dohnal]

Portion of 2-week-old post for context:

>.....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.

There was a long thread on this subject, and I don't remember anyone
mentioning that this information applies to Canadian cars only.  The
American UrS4s are wired differently, with the '85' terminal of the fog
light relay being hardwired to ground.  I'd guess that the Canadian cars
ended up with their 'interesting' wiring scheme when the daytime running
lights were added after not having been originally designed in.

I was following the thread because my relayed high beams occasionally latch
on, and now I'm back to suspecting a sticky relay or headlight switch.  It's
hard to isolate because it only happens to me once every 2 months or so.

Wayne Dohnal
1994 S4