CRAZY_RUSSIAN

Rusty, slightly off the topic question, for the B4 converted to autocheck, which switch should i use? My autocheck keeps buzzing at me when the car warms up at around 2k rpm
thank you

Rusty Spokes

The 2000 rpm warning..either auto-check or the standard dynamic warning system.. would be the high speed oil pressure switch (078919081C) is open circuit (not grounded) at higher rpms.

Could be several issues..first being you don't have 2.5bar oil pressure at 2000 rpm. Most AFC engines make plenty of oil pressure. If you think your oil pressures may be lower at 2000 rpm for whatever reason..use a 068919081D 1.4bar oil pressure switch.

Second issue could be the wire to the oil pressure switch is not connected, loose or there is a break in the wire..That happens many times because of the oil pressure switch location..it is easy to bump the blade connector on the switch during other repairs. If the wire is not grounded to earth at 2000 rpms because it is loose,,the warning comes on.

Third is a defective oil pressure switch..usually they start leaking oil..sometimes they just fail electrically. Could be a wiring problem..not likely..the white/gray wire (check to be sure I have the right colors for oil pressure switch wire on you model car) to the switch can be grounded with a test wire plugged into the blade connector from the switch and grounded somewhere solid..and see if the warning system remains silent at 2000 rpm. If not you have a defective autocheck or a broken wire somewhere.

CRAZY_RUSSIAN

i hope it's not a faulty autocheck)) anyways, maybe i should have given some more background, i got a aux gauge in the middle that works fine, i don't notice any strange dips in oil pressure at different RPM. I just converted to autocheck and i keep getting this buz. as i start the engine, it doesn't go off, as the engine warms up, the RPM level at which it buzzes decreases to where it is at about 2000 rpm at normal operating temperatures.
i don't think i missed a wire while plugging in the autocheck/trip computer, but it is a possibility

CRAZY_RUSSIAN

well, just replaced the 2.5 (078-919-081A) bar with a 0.25 bar(028-919-081D)and the buzing happens sooner at lower RPM now this is frustrating

Rusty Spokes

The oil pressure sender for your aux gauge should have two connections. One is for the aux oil gauge and the other is the .25bar warning oil switch..incorporated into the one sender. So you don't need the 0.25 bar(028-919-081D) switch..it is already in the sender for your gauge. If your oil pressure gauge is working..then you know you don't have the wires misplaced or crossed there..everything there is fine.

If you put a 0.25 bar(028-919-081D) in the loacation for the 2.5Bar switch..you will drive yourself nuts.

Unplug that wire, make a connection lead with a 1/4" male spade connector and plug it into the wire for the oil pressure switch..then ground the other end on the chassis or battery negative post..firmly..it must be a good ground.

See if all the warnings stop with the engine running at 2000rpm+..they should. The system looks for a ground on that wire at about 2000rpm

CRAZY_RUSSIAN

ow, its driving me nuts all right the gauge is perfectly fine about 1.9 bar at idle) thank you, will give that a try here in a bit

hardipk5

Problem was fixed with part number #078-919 081C (red cap) IF i remember correctly it ranged from 2.2 to 2.7
Engine type: 12v AFC from 1995 Quattro

Rusty Spokes

Yep..that is a 2.5BAR high speed switch..which works fine. Most AFC engines will push more oil pressure than 2.5BAR above 2000 RPM.