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1988 Audi 90 Fuse #12 blows...

Old 10-04-2005, 02:20 PM
1st Gear
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Join Date: Jun 2005
Location: Canada
Posts: 32
Default 1988 Audi 90 Fuse #12 blows...

SO, my latest problem is the #12 Fuse blowing, at first once every month or so, now hard short. This results in no insruments, trip odometer, odometer, backup lights etc. I have (finally) ordered a Bentley Manual, but just thought I would put this query out in case someone had a similar experience... any idea where to start looking for the short?

Once I get the manual, it will be leg work to trace the various paths from Fuse #12... still, not something I really look forward to...

Any insight or similar experience would be most helpful and appreciated.

Old 11-04-2005, 06:35 PM
Join Date: Nov 2005
Posts: 12,826
Default RE: 1988 Audi 90 Fuse #12 blows...

#12 15 amp / dash panel / reverse lights / auto check systems / abs / diff lock / computer
Old 11-05-2005, 03:26 PM
1st Gear
Thread Starter
Join Date: Jun 2005
Location: Canada
Posts: 32
Default RE: 1988 Audi 90 Fuse #12 blows...

Problem fixed - wiring short near Speed Sensor, cleaned up, taped, also cleaned / tested Speed Sensor.

Information for others:

This sensor is a 3 wire active device, 12 volts in, ground and centre pin is signal out, apparently an open collector pull down to ground - to test connect 12 volts, ground, then pull up the centre terminal to 12 volts with a 10 K (value not too important) resistor. Centre signal terminal should be a square wave (0-12v-0) as the sensor gear wheel is turned. The output can be observed using a meter or better, an oscilloscope... Sensor couples to an internally mounted gear that turns as the driver's side wheel turns.

Thanks to all for locating this device...

Cheers, Ian
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