1.4 TDI Front Disk Wear Sensor

B

Bato

Member
Apologies if anyone has asked this before but how easy is it to check the disk break ware sensor? I understand it can be affected by small stones jumping up into the wire? Have had new front pads fitted 900 miles back and the warning light came on today for the front disk brakes. MOT was done at the same time as the pads so i assume that if the disks were on thier way out I would have got a caution note on the MOT.

Any help appreciated

Duncan
 
Hi Duncan,

Yes, the wear indicator wiring can be a problem, but not from stones thrown up.

Jack the car up, take off the wheel and inspect the entire wire run from the pad to where the loom passes back into the engine bay.

What normally happens is that the tyre chaffes the wires and wears a hole in them, or, more usually, some ham-fisted mechanic snaps the connector when changing the pads over. As it's only 900 miles from your pad change, I'd suspect the latter is the problem here.

Cheers,

Mike
 
Hi Duncan, welcome to the A2oc
Just adding to Mike's comments, the wear indicator is built into the passenger side inner disc pad. Its just a wire which wears through when the friction material is down to approx 3mm and triggers the warning light. The warning light is not afected by brake disc condition.

Cheers Spike
 
Thank you both for the replys! I will jack the car up after work tonight and see if i can spot the problem.

Regards Duncan

P.S Will post my findings on this thread!

Ok problem sorted, it was the sensor where it plugs into a wire that come out of the brake not directly into the brake its about 3 inches back but behind the wheel. Didnt need to take the whole wheel off just jacked it up and used a Headtorch / shaving mirror to see it and Bobs your uncle problem solved and I didnt even find a place to use mans oldest solution to a problem.... Gaffa Tape!!

Cheers Guys
 
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Hi,
I had a beep less than two weeks ago and had to search the owners manual to check what it is. It was the brake signal so I had a full service of brakes in a garage nearby. I have now new discs and all. However, even with the new discs the alarm of brake wear is still popping up.

I checked the female cable end of the brake sensor and it is at 0 ohms. I assume this is a normal condition for new units. I have also tried short circuit the vehicle-side chord that has those two male pins as seen in the picture. The situation is still the same. Beep comes immediately.

I also noticed it behaves differently than before the service: I had first the OK and then after a couple of seconds the beep. Now after service no OK, just the beep immediately - even when short circuiting the pins. Maybe some of the wires have broken so the circuit is fully open.

Does someone know the electrical operation principle of the brake sensor? I would assume it's a simple short circuit system that is eventually broken by the use of the brakes. And then the signal comes. Am I close? Where is the other end of the wire so I could check the circuit is working? Any help appreciated, I'd like to see the outside temperature once again :D
 
Agree with above.

After my serivce, having had brake disks replaced, the disk pad symbol flashed up soon after. It was easy to see the problem without jacking up the car, as the small wire behind the wheel going into the brake pad had come loose. Was a quick repair.

I think if the pads are worn, you should hear them make a noise as a piece of metal becomes visible and it makes a noise against the disks.
 
brake wear indicator !

has anyone actually had this work as a result of wearing pads down to 3mm..?

my current O/E Audi Disk Pad combo seems to be nearing the wear limit on the disk but there's loads of meat left on the pads.

Is this common / unique to this particular set of friction materials.

I'm going with Mintex boxed set for the replacements

P
 
Are you sure it's the brake pad sensor. It could be the abs sensor as the sybol is very similar on the dash. The Abs cable's also get worn by the tyres on 17's.

On mine I had to change as the copper became exposed and then water ran down the cable into the Abs sensor and corroded it. This made the symbol on the dash light periodically and the associated warning beeps.

Nick
 
Good point, I checked this post with the warning light shown in the first picture http://www.a2oc.net/forum/showthread.php?t=13117&highlight=abs+dash. It's not this one. It's a yellow ring with these 6 short bars surround the sides of the circle.

I had a quick check from elsa. The yellow cable in my picture should be ground and red is going eventually to ecu. Maybe I proceed by checking first the ground contact and if that is working then the red chord. If understood it right, it should have a contact in A pillar connector.

Let's see what I can find out.
 
Found the problem source today: The ground wire is OK but the red chord has no contact with the other end at the A pillar. I double checked that the error message on the dash is gone once the red wire on the A pillar is short circuited to the ground.

So in my case the problem reduced to finding the way to renew the wiring. I Couldn't find any point on the chord that could potentially explain the issue. Whole cable looks just fine. I wired a new cable next to the old and guided it out from the wheel case. Try to attach it to the original one far enough so hopefully I'm lucky. Otherwise I need to extend the new chord all the way to A pillar :(
 
Got it finished today. I soldered the new chord to the old one at where the wires go inside the car cabin top right corner under the engine bonnet.
I noticed before that copper of the pad sensor wires inside the wheel house was quite black. I mean the wires were badly corroded. Now that I cut the same wire quite distant from the wheel house (shown in the picture) I found nice and clean copper chords: It looked the same as it was wired yesterday. So there must have been a leak in the wheel house that I couldn't locate.

Unfortunately the camera battery run out so couldn't take a second picture :)
 
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