Brake Pad Light - "Corroded Loom"

[JogoRS4]

Hello All

Has anyone had this one from Audi?

My brake pad warning light comes on intermittently and can often be reset by turning the ignition off and on again.

The pads still have 60% left in them and the discs are only about 8000 miles old - so all in good shape.

Audi have told me that the wiring loom is "corroded" between the sensors wires and the control panel.

Not sure how the copper wire can corrode!

Has anyone else had this?

Mileage is around 58k

Thanks
http://forum.rs246.com/posting.php?mode=post&f=35#

[adsgreen]

The cable sheath covering the wires can wear. If this happens then the wires will short and make a circuit tricking the ecu into thinking the pads are worn.
(normally the two pins will be buried in the pad material and when they poke out and touch the disc a circuit is complete and warning set).

[Ranger Rico]

I'm having exactly the same issue at the moment, I changed the discs and pads myself a few months ago so assumed I must have bodged the job somehow and maybe damaged the pins on the pad connector, was gonna have a look when it gets above 0 degrees!!
This only started after the pad change so I don't think it can suddenly be corrosion.

[JogoRS4]

I had a chat with the technician and he reckons its the pins in the socket that are corroded - they won't clean them of course as they want to sell you new - so like you I'll take a look myself and give them a good clean..and coat the sockets in silicone or some such to protect them - of course now i have the car back from Audi the warning light is now on permanently rather than intermittently ....;

On another note my exhaust valves are seized solid so its Miltek here we come!!!

[Ian_C]

The cable sheath covering the wires can wear. If this happens then the wires will short and make a circuit tricking the ecu into thinking the pads are worn.
(normally the two pins will be buried in the pad material and when they poke out and touch the disc a circuit is complete and warning set).

Isn't it the other way around - two wires go into each pad and join in the pad material, as the pad wears the wire in the pad breaks and the circuit is broken which puts the light on?

Pretty sure its this way round (warning light comes on when circuit is broken) because I've removed the wires from the pads on mine..... (B6 S4)

Had this issue last year before Le Mans and my mot - dash light coming on - pad thickness okay - but warning light is an mot failure nowdays! Removed wheel and found one of the wires had detached from the pad, so I also removed the other wire going into the same pad, reduced the length of the wires, stripped the last inch to wire bare, wound them together and then wrapped them up to complete the circuit (bypassing the pad). Dash light disappeared. Had been fine since until the pad light came on again over Christmas, imagine one of the wires going into the three remaining pads has now come away too, so I've got to dig the trolley jack out the garage and do the same again

Imagine the B6 S4, B7 S4 and B7 RS4 use the same warning system?

[PetrolDave]

imagine one of the wires going into the three remaining pads has now come away too.

IIRC the pad wear wires are only on one pad each side at the front, i.e. only on 2 pads.

[Ian_C]

Yes that would make sense - I could only see wires going into the inside pad, not the outside

[Ranger Rico]

Intermittent Pad warning light has been annoying me since I fitted new discs and pads a few months ago, If I switch off then on once maybe twice it goes away!!!
yesterday it was Dry enough to remove the wheels and get into the brakes, Would have to agree with Ian above, I'm sure the pads create the circuit, a worn pad will break the circuit, couldn't find anything obvious, unclipped the sensors and sprayed some wd40, started her up and got an ok, brilliant.
Started this morning to the warning again!! Really pissing me off now.
I'll get a multimeter on it later and see if I can locate the break.
Has anyone solved this common problem? I've done a search but no definitive answer.

[adsgreen]

ah ok - different from ye olde brakes I saw that had these

[guffy]

I have this as well, just appeared when changed the discs and pads recently, normally when it's wet too.

They do fail under an open circuit, so not sure how the corroded loom idea works?

Originally I thought it was the pads, so i used the plugs from the old pads with wires crossed together, but i still get an intermittent warning

The downside of older cars in wet climates!

[Ranger Rico]

Yeah and it's hardly ever wet in Aberdeen

What I'm going to do next is remove both wheels and start the engine to get the warning light then remove the pad wires and using a multimeter see if I get continuity up through the loom, I'm thinking if one of the wires fails at least I've isolated which side the faults on.

I really don't want to take it to a garage, fault finding is always expensive.

[Timster]

Pad sensors are only on the fronts and throw an error when open circuit, not as stated above.
Dampness can get in the connectors and give an intermittent error. Some WD40 may help repel the moisture.

Removing the flying-lead from the pads and bridging the pins on the socket will fool the car into thinking everything's ok.
(just remember to keep an eye on your wear as obviously you’ll no longer get a warning when the pads are low).

Also trying giving the car some spirited braking to clear any crap after new pads.... that can help.