adie68 Posted February 21, 2007 Report Share Posted February 21, 2007 Need some advice please.. My 1997 A8 4.2 Quattro has recently had new disks and pads all the way around. Since having them fitted the low brake pad warning light has come on. At first assumed it was a problem with the sensor wires in the new pads so had a second new set fitted. The light remains on... Full diagnostics by my local specialist has not shown any sensor or other faults... They are suggesting that I may need to replace the fault display ECU as this is the most probable cause of the problem but this is going to run into the £000s... Has anyone else experienced this problem and if so can they offer any other possible causes or suggestions. Thanks in advance Link to comment Share on other sites More sharing options...
Atomic Posted February 21, 2007 Report Share Posted February 21, 2007 Seems a daft question but are the pads the right ones? and has someone checked to see if the sensor wires arnt broken/chaffing. Link to comment Share on other sites More sharing options...
adie68 Posted February 21, 2007 Author Report Share Posted February 21, 2007 The pads were supplied by Eurocarparts, I can only assume they are the right ones as it was the only 4 pad per disk fitment with sensor wires that they stocked Been to 3 different places now and on 2 different diagnostics systems. My usual garage has and the wheels off and checked the connections.. But no harm in taking it back and getting them to check the actual wires. Link to comment Share on other sites More sharing options...
rob77 Posted February 21, 2007 Report Share Posted February 21, 2007 be careful with aftermarket pads they squeal like a pig,i dont know what causes the problem but it did my head in and i took them out and replaced them with OE pads,that was on my 2.8 sport which never really took a hammering but theres no way i would put them in my S8 Link to comment Share on other sites More sharing options...
ghemmings Posted February 21, 2007 Report Share Posted February 21, 2007 I had exactly the same problem recently. It was a break in the wire loop from the pad sensor connector to the car. I just cut the wire near the car chassis, twisted and soldered them together. Problem solved. That was the offside wiring, but the nearside will still work when the nearside pad runs low. Link to comment Share on other sites More sharing options...
drmotorsport Posted February 22, 2007 Report Share Posted February 22, 2007 I've had exactly the same problem with the same 4 pad brake setup. In my case it seems the pads just needed to bed in properly and over some 200 ish miles the warnings got fewer. It maybe worth waiting for a few miles before looking for other problems! Link to comment Share on other sites More sharing options...
ronmcl Posted February 22, 2007 Report Share Posted February 22, 2007 This section on Audipages might help?... http://www.audipages.com/Tech_Articles/susp_whls_brake_steer/brakesensor.html Link to comment Share on other sites More sharing options...
fudge Posted February 22, 2007 Report Share Posted February 22, 2007 Most brake warning systems put a light on when the (single) wire to the brake pad is earthed - this occurs when the brake pad wears sufficiently for the sensor wire to touch the metal disc and short to earth. Audis are more sophisticated; they have 2 wires in a loop with a small current flowing through the loop to keep the warning light out. When your pad wears the loop in the pad wears through breaking the circuit and the light comes on. This means that the Audi system "fails safe". In the non-Audi system a break in the wire prevents the warning light ever coming on (it cannot earth at the pad) so you get no warning. The trouble is that the Audi system can and does give false warnings. In my experience this is usually caused by either: (1) A break in the wire leading to the sensor in the pads or (2) A dirty plug socket causing a bad connection. If you have an electrical test meter you can easily check the pad sensor by unplugging the connector in the wheel arch and ensuring that there is continuity (low/no resistance between the two pins in the pat of the socket connected to the pads). You can check the wiring back to the car by shorting out the pins in the part of the socket connecctor that leads to the car (the warning light shoud be out when the pins are shorted). If you remember that the wire flexes each time the steering is turned breaks can occur in the wire. In your case, because you had no problem before the new pads my first check would be that the connector is clean and properly seated. Link to comment Share on other sites More sharing options...
adie68 Posted February 22, 2007 Author Report Share Posted February 22, 2007 Thanks for all the advice guys... I did drive 150 miles yesterday and the light stayed out for about 100 of those.. until I pulled on tho the drive and it came back on... Looks like the weekend might be spents with some electrical contact cleaner and and electric test meter... Link to comment Share on other sites More sharing options...
ronmcl Posted February 23, 2007 Report Share Posted February 23, 2007 [ QUOTE ] until I pulled on tho the driveway and it came back on [/ QUOTE ] That's significant and suggests that Richard is spot on. Is it likely that you turned the steering a lot sharper when going into your drive than you had when driving normally for the 100/150 miles? Probable that you have an intemittant bad connection that is triggered by, for example, putting the steering onto full lock. At other times, after driving for a while, the general movement of the steering may allow the connection to be re-made and hence put the light out again until the next tight manoeuvre. Link to comment Share on other sites More sharing options...
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