Re: Electrical gremlins (elves?)

[Elliott Potter <epotter@abraxis.com>]

Chris Newbold wrote:
> 
> Looks like the Audi Santa, er God, of electricity has come early this
> year... I've got some weirdness with things driven off the driver's door
> jam switch.
> 
> As in most Audis, the driver's door jam switch drives a number of things:
>   o dome light
>   o radio on binger
>   o lights on binger
>   o alarm
>   o interrupt power windows (first time door is opened after ignition
>     switched off)
 
Ooh, your power windows thing works?  Mine never has.

> In the last few days, things haven't worked right; at first I figured
> that the switch must be worn or corroded. However, I've noticed that
> the failures affect a random collection of the items above.
> 
> Tonight, for example, the dome light did not go on when I opened the
> door, but the lights-on and radio-on binger worked, and so did the
> power-window interrupt. This morning, I had dome lights, but no
> binger.
 
Do groups of features seem to be mutually exclusive?  i.e. if you have
dome lights you definitely won't have the power-window interrupt?
When the dome light doesn't come on, have you tried opening other doors
to see if they'll turn it on?  Also, for the power-window interrupt,
have you tried windows besides the driver's window (including the
sunroof)?
This could be a good use for the wiring tracks section of the AllData
CD.  There's a ground point somewhere, I think it's way up near the
firewall on the driver's side, that has 4 or 5 lugs coming off of
it--might check to see if that's tight.

> I've also noticed that the seatbelt binger is flakey; if you start
> the engine without the driver's seatbelt buckled, you're supposed to
> get the red idiot light and binger for ~15sec. However, I usually
> get one or the other, maybe neither.
 
My seatbelt light comes on regardless of the state of my seatbelt (or at
least I think so; I always have it strapped in when I start the car) but
I don't hear the chime.

> Any ideas? At first I'd suspected the door switch, like I said. That
> doesn't account for all of it, especially the seatbelt binger. I also
> suspected the binger itself (bad connection in instrument cluster),
> but that doesn't explain the dome light behavior. Bad ground? But where?
 
Look up around the driver's footwell, kinda behind the relay rack--I'm
pretty sure that there's a big grounding spot there.  Also check that
AllData CD for locations of what controls the various things.  My guess
is that they have a common ground (very likely) or a common power bus
(merely possible).  If there's something that's located near the ECU, it
might be a corrosion problem--that's right under the A/C compressor, and
things get pretty wet--my ECU case is rusted shut!

> Any thoughts on where to begin from the reigning Audi electrical
> exorcists would be appriciated...
 
Sacrificing a goat?  :)
Seriously, look for the big grounding point, or possibly (ooh, ooh!) I
think there's a large multifunction relay near the driver's left knee
that does a lot of this--can't remember which one it is exactly, but
there's a sticker that shows (vaguely) which relay does what.  Possibly
the big flat one to the right of the airbag relay.

> -Chris
> 1993 90CS 5spd 71k miles

-- 
Elliott