<E30> Weird Headlight Problem Fixed (or is it?) <long>

[Scott Miller <sdmiller@xxxxxxxxxxxxxxxx>]

Part 97 of 97?  Wherein I share my embarassment in hopes that it will
keep others like me from making the same mistakes.  (It is arguable that
there are no others like me, but let's not go there right now, OK?) 
Let's start with this premis:  If it walks like a relay problem and
talks like a relay problem, it is probably a relay problem.

To recap as succinctly as possible:  Problem was, when switching from
high beams back to low beams, about 25% of the time all headlights (and
foglights) would just go completely out.

Had tried:  Switching, then replacing relays (more on this in a moment),
and replacing the turn signal / high beam combination switch in the
steering column.

So today I thought I'd look in the fuse box for bad connections and
such.

Step 1:  Verify that the headlight relays were the ones I thought they
were.  Removed what I had thought were the low beam and high beam
relays, verify that lights no longer work - OOPS, what's this?  The
lights still work!  Well, it seems I replaced some perfectly good
relays.  OK, swap them out and put the old ones back in (had kept them
as spares).  Note:  I had gone by the Bentley manual in determining,
incorrectly, which were the headlight relays.  Well, it's right there in
the manual, a very plain YMMV warning.  And besides, I should have known
better (you don't want to hear the story about how I replaced a
perfectly good alternator and voltage regulator in a 1974 Opel when all
it needed was a fuse, because the Haynes manual misidentified the fuse
assignments - see, I've done OOPSes before).

Step 2:  Now actually FIND the right relays.  Just started pulling them
one at a time until, behold, when I pulled the PURPLE one, highs, lows
and fogs stopped working.  Interesting thing, that purple relay, it had
5 contacts.  The low beam, fog and horn relays had just 4.  I distinctly
remember a Digester (forget who, it was a long time ago) telling me that
I would swap headlight and horn relays as a test.  Well, I guess I
interpreted that to mean both high and low beam relays, while it is just
the lows.  Of the 8 relays in my fuse box, only the high beam relay has
5 contacts, and guess which one I don't have a spare for?

Step 3:  Reflect on the wiring diagrams which Ron Stygar had sent me. 
Note:  Several people faxed or e-mailed me wiring diagrams from various
years of E30s in an effort to help.  We then discovered the differences
in wiring between the cars with ellipsoids (1988, 1989 E30) and the cars
without (including 1987 and 1990 E30).  Turns out, of the ones I
received, the 1987 diagram matched the way my headlights were wired.

See, in a 1987 325e or 1990 325i, the circuit that powers the low beams
and fog lights gets it's power fed through a normally closed contact in
the high beam relay.  When you power up the high beams, the high beam
relay switches off the normally closed contact and switches on the
normally open contact, which basically diverts power from the low beams
to the high beams.  All 7 of the other relays in my fuse box have only
contacts that close when the relay is powered up.  The high beam has
both normally closed and normally open positions.

Step 4:  Check the relay contacts.  Well, what have we here?  Contact
87A, the normally closed contact that powers the low beams, is RUSTY! 
Ah ha, I believe we've found our culprit.  Cleaned the relay contacts,
cleaned the socket connections in the fuse box, replaced the relay.  

Step 5:  Test it.  After about 50 cycles of the high / low switch, NO
FAILURES!

What else did I do wrong?  Well, I had 7 very plain, normal looking gray
and black relays that looked right at home.  Then I had the PURPLE
relay, the one that stood out like a sore thumb, the one that said,
"Hey, I'm different, I'm unique, I don't match the others, I MAY HAVE
BEEN REPLACED BEFORE, MAYBE YOU SHOULD CHECK ME FIRST, DUMMY!"  And I
totally missed that little hint.

And what else?  Well, why was just that one contact rusty?  This usually
means moisture has been present, but none of the other contacts were
rusty.  Is this an indication of a bigger problem?  Probably, but I'm
not ready to deal with that today.

Anyway, as the saga winds to a close, thanks to everyone who helped with
advice, wiring diagrams, etc.  I really do appreciate that this Digest
is a vaulable resource, and not just a cheap form of entertainment.

Scott "I should know not to believe everything I read" Miller
Golden Gate Chapter
BMW CCA #44977
1990 325i/is with headlights working again

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