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Re: S4 Relay Chatter Gremlin
Over the past few months, it has developed a really annoying and peculiar
electrical gremlin. With the ignition off, relays inside the dashboard
start chattering and clicking wildly. If the windows are down, they roll up
I've noticed that the window power doesn't always shut off like it's
supposed to when you open the doors. Sometimes it _does_ shut off, then
turns on by itself later.
The only reliable way I've found to silence the noise is to pull three fuses
from the box in the engine compartment. If I don't, car will try to roll
the windows up from time to time, draining the battery.
The dealer claims he can't find anything; I don't blame him because the
problem is very erratic. Sometimes it goes days without malfunctioning.
Other times, it starts up in the middle of the night and sounds like a ghost
moaning in the garage.
Wow, that's one my UrQ has thought of yet . . .
My immediate guess would be a loose wire that is either completing a ground
connection ("shorting") switching on a circuit, or a stuck relay providing
power after you switch off.
About the only way you will likely find it is to start taking things apart
and poking/prodding/pulling/wiggling/and-otherwise-perturbing the wires and
connections till you find it. Look for "obvious" things (hot relays that
should be cold hours after power off, melted fuse boxes [the box in my UrQ
melted around the rad fan fuse, which caused it to "sag", intermittently
powering the rear defrost circuit, which in turn backfed the whole load-
reduction circuit, empowering the A/C/fan/etc...which of course killed off
the battery yet again...], etc.). You may be lucky and find a very-ob-
viously charred/melted/broken/dangling wire/connector (if you touch a
wire and it turns into dust in your hand, be very suspicious...).
By approaching the problem logically and methodically ["if I were an Audi
out to get my master, what would *I* do..."], you should be able to narrow
down and eliminate about 90% of the wiring harmess [sic]. For example, what
fuses do you remove to "cure" the problem? Which fuses feed, and which fuses
are fed by what? (You'll need the wiring diagram!) At what point could you
supply power to a circuit ("short to ground to switch on a relay", or "short
to an adjacent +12 to feed a circuit") that would match your symptoms? [This
exercise alone can occupy you for many nights to come!] When relays start
chattering, can you pull one of them to cure the problem? With a voltmeter
in hand, what circuits seem to have power when you think they shouldn't
(cigarette lighter? rear defrost? fan? seats? radio? wipers? blender?).
Generally, these types of problems are a "single point of failure", are when
finally [whew!] identified very simple and obvious, and are trivial to fix.
But they can take hours, days, even *weeks* to diagnose and identify. It may
take you 10 or 20 "experiments" to track it down, spread out over weeks of
waiting for the symptom to recur/reproduce. Keep careful track of what you
can positively eliminate. Eventually you will have eliminated everything
except the problem component. When you have eliminated all possible com-
ponents, iterate the whole process again, 'cuz you missed it the previous
'n' times through.
And Gawd have mercy on your soul if you have two (or more!) interacting
problems mutually masking each other . . .
This is the proverbial thou$and$ of labor to find the $3.76 part to replace.
Good [cough cough] luck!