Brake Pad Warning Light

[jarnold231]

So brake pad warning light came on yesterday. Visual inspection suggests they're all good, I haven't noticed any decrease in braking performance, and the discs aren't marked outside/inside that I can see. All of the brakes were changes <3000miles ago (all new calipers / pads / discs) and I don't tend to be particularly heavy on the brakes.

All of this leads me to conclude its a sensor issue. I've had the car up and had a look at the connections on the front pair which appear to be in place and properly seated, but the error light persists.

Anyone got any ideas or quick fixes that can sort the error light issue?

 

[Charlie Farley]

Yet another common failure point, check the wiring on the pad wear leads and plugs, they have a habbit of breaking internally , very sutle breaks aswell, worse case just loop back the lead so it show the pads are new.

 

[Charlie Farley]

I've not had oem caliper/pads on my old bus for years now but from memory the wear leads are fixed to the pads so you'll need to disconnect the plug from the main loom and get a multi meter the lead to see if it shows up as faulty circuit between the pad and the plug.
I'd just cut of the pad lead and convert the lead and plug into a loop back plug and refit thus taking the pads out of the circuit.
Just means you'll need to check the pads yourself for wear, which is allways best really.
My 18z's use replaceable leads that push into the caliper , just replace the lead and plug when required, that said I had the same issues with mine so just looped back the lead , end of problem.

 

[jarnold231]

"I'd just cut of the pad lead and convert the lead and plug into a loop back plug and refit thus taking the pads out of the circuit.
Just means you'll need to check the pads yourself for wear, which is always best really."

If it makes a difference they're Brembo pads on the front?

Looping the plug does seem to be the best solution, so theory is:

1. Cut the brake pads female connector off
2. Solder connections together
3. Heatshrink the connector up
4. Reattach newly bodged loop back plug to sensor connector

 

[Charlie Farley]

pad brand makes no difference with the oem setup.
Yep, just cut of the cable at the pad, and then cut to a length of your choice , join up which ever way you wish, refit the new loop back plug/lead, job done.
before you do though ,just check the circuit with meter to ensure it is a cable break, on either one or both sides.

 

[jarnold231]

Thanks Rob, whilst it's unlikely - is it possible that the sensor cable on the car itself has shorted out?

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[Charlie Farley]

There are two possible point to check, the plugs and the lead, just working back from the pads to the connection plug will show up where the problem is.

 

[Sidrick]

Brembos come with sensors.

 

[jarnold231]

Brembos come with sensors.

Apparently not infallible ones though

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[Charlie Farley]

Brembos come with sensors.

None of them have real pad sensors , they are just open circuit detection on the pads, when the circuit is broken by the discs wearing through a small piece of wire in the pad the circuit is broken and the error light is illuminated.
If the pads are good then the fault can only be in the wiring to the pads, weather its from the connection point , the wire or further back , that why its best to check first for an open circuit.

 

[Charlie Farley]

I had a break in the wiring just where it leaves the plug , tiny break but enough, and the leads were only not that old.
taped up area in pic.

 

[jarnold231]

Success!

Had some old brake pads so I chopped the ends off them, soldered the wires together, electrical tape, gaffer tape, unplugged actual brake pads, installed bodged connectors and problem is gone.

Thanks all for help

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[Sidrick]

So the warning light no longer works?

 

[jarnold231]

Well the warning light works, it's just that the connection it's attached to is now permanently saying "Saul Goodman" and I shall have to check my brake pads like a responsible human.

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[Mike B]

The false warning is a nuisance .Just bridged the sockets on the pads with a piece of a paperclip and taped over.You get a lot more wear out of the pads and its simple to look at them through the wheel and check the wear .I think the light is now a MOT failure now which is daft if the pads have loads of wear left

 

[Sidrick]

Would it not set alarm bells going for anyone else if they bought a car and found the brake wear warning system bodged/bypassed? Just me then

 

[Charlie Farley]

Maybe if audi had put a bit more design thought into it owners wouldn't have to make work arounds to solve a problem that could have been avoided to start with.
It really isn't one of there better design frankly, it maybe simple in operation but also very unreliable in operation.
Pads should allways be checked manually rather than just waiting for a light to come on , I was allways taught to check these things manually and on a regular basis.
Just common sense really, but some owners just rely on warning lights before checking for wear and tear items such as pads and low tyre pressures etc.
I'm not saying everyone can check some items but a quick stop into a local garage would allways be beneficial .
anyway just my input.

 

[Sidrick]

Pads should be checked manually at service and MOT times, even if the vehicle owner doesn't check them him/herself in between. The light is a fallback, a safety, not the single deciding factor of a parts health.

See also: Fuel light, ABS light, CEL light, Oil light, Seatbelt light, etc, etc.

Splicing the wires is a bodge. The fix is replacing the wear sensor (in most cases, or tracking down any other problems).

I'm maybe viewing these old cars slightly differently. I like mine and the DTM shouldn't lose much, if anything, in value if kept legit. If you just plan to run it into the ground, fair play.

 

[Charlie Farley]

So what happens then when a owner of a let's say well cared for B7 , has a low pad light come on one day and they are not a diy hands on mechanical type person.
They book into let say an "audi garage" to be checked out, audi check it out and say it needs new pads etc when in fact the pads are actually fine but the problem is the cable , as we know, but they wont fix that itself.
Instead they will replace the pads that are not in need of replacing, just a dash low pad warning lamp says otherwise.
They will charge the owner for a new set of pads at audi prices plus labour all because of a small piece of wiring that has failed with nothing wrong with the pads and no effect on the cars safety whatso ever.
Now that's wrong and all down to the design , not all pads have replaceable sensors so the owners are stuck.
I had it twice on my original calipers which didn't have removeable sensors , and twice on my 18z's , but at £25.00 a go for the sensor when the pads are 70% material left is just not acceptable frankly.

 

[Sidrick]

So it's all based on taking your car to Audi and being told you need new pads, rather than the likes of kwik-fit and being told 'your pads are fine, ignore the light until next pad change'? Gotcha.

 

[Charlie Farley]

That was an example and could be applied to any garage really, depends on there policy for repairs wouldn't you agree.
Audi wont fix the lead full stop, they will just replace the pads even if they are nearly new, other independent garages may fix the lead or maynot all down to them.
My point is that the design is flawed ,well on B7 to start with , as there is no allowance for the lead or plug failing so parts would need to be replaced at cost to the owner and in many cases the pads are not at fault.
It's a subject that could bang on forever but wiring out the open pad circuit is not a botch , its a simple solution to a problem that effects many owners to a more or lesser degree, it is an irritation and possibly expensive repair that is just not required.

 

[jarnold231]

The way that I did my bodge (took connectors off an old set of pads, bodged them, reinserted them into sensor connector) doesn't preclude going back to sensors when I change the pads next time round.

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