Completely unpredictable! Comes on at any time/ any rpm, comes and goes as it pleases. Console-mounted gauge ALWAYS consistent with engine status. I changed the sender (on the cylinder head) and no effect. I even disconnected the thing at the sender and it still activates!
Only time it's been of any use was when it came on immediately a coupla months ago and a quick check of the gauge told me "pressure drop", seemed the oilcooler on the filter housing blew out its rockhard O-ring that nobody ever thought to change before my daughter bought this car!
Anyway, hope someone can zero me to the fix... '85 4000s 1.8 auto, we both still love this car but man...
Thanks!

<center><img src="http://pictureposter.audiworld.com/2705/dsc00020.jpg"></center><p>My first CGT did the same thing. I replaced the sending unit, no good. It's pretty common I hear. So I just pulled the buzzer out of the fuse panel and was done with it. My current CGT, pictured above, only has 45,000 miles on it, so it's still behaving.

Mine did it all the time too. i pulled the buzzer unit out and clipped the buzzer wire. now the light just comes on but i've learned to ignore it. i should just take it out, what good is a light that doesn't mean anything?

clean them all up
and most importanlty,, get a new heavy duty ground wire to teh battery, or resolder teh connections whin the crimp. works wonder,, Mine has not busszed for 5 or 6 years now.

Thanks for the advice here!
I can replace battery ground cable and redo the sender spade no problem, but warning light/buzzer still active even when sender disconnected! I haven't ripped into the dash yet but can anybody direct me to the location of the buzzer?
Also, although it's woefully inadequate for an '85 model, my Haynes manual shows a "oil pressure warning light control unit" in the wiring diagram for an '82. Is this the buzzer, where is it located, could the ground problem be there?
Thanks to all!

OK, some light at the end o' tunnel here... removed instrument panel cover to see what's under there, nothing under there looking like an oil pressure controller whatever that looks like.
Went below and there under the dash, up in and behind the cubbyhole in the dash to left of steering column, is a bank of 3 plug-in devices! First one had holes in the end &amp; as I had the door open and key in ign chime was ringing away so this one revealed itself. I'll be modifying that one soon... Next shorter one is I dunno what, next space (of 4) is empty.
Fourth one when pulled not only was diagrammed with symbols similar to the "controller" diagrammed in Hayne's but numbered contacts ID'd it as my target (my very rusty German helped here also...). Yanked this baby and went driving.
Result: Key on, oil light on and gauge 0. Start engine, light goes off and gauge cranks up to max (drops to 2-bar after warmup). Driving about ten miles, gauge responds accordingly and NO IDIOT LIGHT or BUZZER ACTIVITY WHATSOEVER!
I know this is longwinded but I gotta ask, is this Controller simply tied into the oil pressure light circuit to activate the warning buzzer, is IT the buzzer? The light seems to function independently, without this device installed everything appears normal.
Best thing about Bosch components is that they can be disassembled usually and "tidied up" mechanically, and if this is the buzzer unit I would prefer to keep it (functioning properly) as this is my daughter's first car and an audible alert is a little extra insurance. But if it needs replacement and carries a Bosch K$$$ pricetag, I would probably be happy to rely on the apparently still-operative $5.00 sender/light system and teach her to gauge-scan!