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Con-fuse-ing info

Going through the dealer's work orders that comprise my "new" '91 200q's
service history, I came across a puzzling episode:

Seems that the PO brought in the car complaining about poorly running
engine. The Audi technician toted up about $130 worth of diagnostic labor
plus a parts charge of about $2.50. He stated in his report that he found
that fuse #24 was _missing_. "Replaced fuse, car runs fine now."

Hmmmm, I wonder: What _is_ fuse 24? According to the list on the fuse box
cover, fuse #24 is "not used"! According to the '91 200q Owner's Manual
it's again stated to be "not used"! According to the fusebox description in
the front section of Bentley Manual (vol. one), it's still "not used".
Three strikes and you're out, right?

I therefore smugly concluded that the dumb Audi tech had replaced a
*non-functional* fuse! And claimed it solved the engine problems! What
gives here? Read on.

While perusing the Bentley manual one evening last week (yep--probably
waiting for Seinfeld), I came across the diagnostic procedures for the
charcoal canister frequency valve (page 24-110-1). If there's a negative
response to a test procedure, it states: "check fuses 24 and 28".

Whazat???? Fuse 24?

So I next went to the wiring section for '91 200q 20V, and there (page
529), fuse 24 is clearly labelled as "electronic injection system".
Locating the carbon canister freq. valve on the wiring diagram eventually
led to the fact that fuse #24 is required for operation not only of the
carbon canister freq. valve, but the *idle stabilization valve* and the
*wastegate frequency valve*, as well. BTW, fuse 28 is for the Motronic

I suspect the PO needed a spare fuse--saw a presumably "not used" fuse in
slot #24--and pulled it to use elsewhere. Who knows?

Anyway, I learned (a) don't be _too_ quick to criticize the "monkey lads";
(b) don't believe _all_ of Audi's technical information; and (c) read on.

Phil Rose		Rochester, NY
'89 100
'91 200q		pjrose@servtech.com