Brake Pad Wear Indicator

[BigDog]

My brake pad wear indicator has come on but intermittently. According to the handbook only the front brakes are equipped with wear detection, and I see on the fronts, only the NSF wheel has it. The front pads have 8-9mm wear left.  Since it works by breaking a wire embedded in the inner pad and that should be permanent until the pads are changed, I am figuring there is a problem in the wiring. 

 

I've seen on other posts that later cars have pad wear sensing on the back too.  My rear outer pads are down to about 3mm and the discs are looking pretty ropey around the outer edge. Now, it is pretty difficult to see whether mine has rear pad wear sensing or not without taking the wheels off, and its not clear whether the wiring is with the ABS - there are three things leading to that area:

1) hydraulic pipe

2) handbrake cable

3) ABS sensor cable (possibly combined with pad wear)

 

A couple of questions so I can gauge the urgency here:

 

• WIll the car go through the MOT with the pad wear indicator lit, even if the mechanic can see the pads are OK and brake test is alright?
• Anyone know if mine has rear pad wear sensing ('53 plate Alhambra TDI 115 AUY, basic spec.) to save me taking the wheels off and then putting them back on again to go and get the bits when they are needed assuming the Mrs is out in the other car (ok, maybe I am getting a bit lazy here)?

Many thanks,

 

Matt

[SilverBeast]

I have a MK II Galaxy and it has wear sensors on both front wheels and on the drivers side only at the rear. My light comes on occasionally and though all the pads appear fine. I suspect dodgy wiring somewhere but it's never been on long enough to diagnose.

 

Does anyone know if VCDS Lite can tell you which pad it thinks is low?

[acecard]

I have a MK II Galaxy and it has wear sensors on both front wheels and on the drivers side only at the rear. My light comes on occasionally and though all the pads appear fine. I suspect dodgy wiring somewhere but it's never been on long enough to diagnose. Does anyone know if VCDS Lite can tell you which pad it thinks is low?

same here- light started coming on intermittently- rear pads fine - changed front pads as they were wearing but not that low - after change light coming on intermittently again for a few weeks, then it stopped - never found out why

[daddyfixit]

1. doesnt it have a sensor in offside rear pad ????   sure mine has?

 

2.any  brake warning light on is an mot fail now.

[MadBaz]

Definitely a sensor in o/s/r pad and iirc o/s/f. I have had the rear pad cable break right on the connector easily fixed by soldering the connector off an old pad and with a bit of heat shrink tube.

[BigDog]

Many thanks gents, It didn't come back on since posting, and 2 or 3 short-ish trips.  I am going to see how it goes for the few weeks before MoT time, and give the weather a chance to warm up maybe.

Matt

[acecard]

I know its not 'politically correct' but  with an intermitent bulb warning (though you have checked nothing is wrong) which may cause an mot failure, it may be wiser to disconnect the bulb temporarily.

Flame me if you  want but you've got to be realistic now with the severity of the mot tests

[BigDog]

Acecard, I share the sentiment but sometimes it's not that easy - many dash warning lamp clusters carry LED lamps these days and then there's the eagle-eyed tester expecting to see lamps lit in the "bulb" test upon turning on the ignition. Mine beeps when the brake pad wear LED(?) re-lights too after start-up, Just my opinion, but with many faults of this type it could be easier for those of us lacking a sympathetic tester to solve the problem in the first place rather than go messing with the dash insert panel - and I'm a sparky (of sorts). 

 

I'm pretty sure sure the faulty wiring is going to be in the bit(s) that gets flexed every time the suspension or steering moves, the Honda which the Mrs. had went through a few ABS sensor cables in the same way.

 

Matt

[acecard]

Acecard, I share the sentiment but sometimes it's not that easy - many dash warning lamp clusters carry LED lamps these days and then there's the eagle-eyed tester expecting to see lamps lit in the "bulb" test upon turning on the ignition. Mine beeps when the brake pad wear LED(?) re-lights too after start-up, Just my opinion, but with many faults of this type it could be easier for those of us lacking a sympathetic tester to solve the problem in the first place rather than go messing with the dash insert panel - and I'm a sparky (of sorts). 

 

I'm pretty sure sure the faulty wiring is going to be in the bit(s) that gets flexed every time the suspension or steering moves, the Honda which the Mrs. had went through a few ABS sensor cables in the same way.

 

Matt

Yes you're right about the difficulty of isolating an individual warning light - wasn't thinking clearly at the time (tescos dark rum)

However, I cannot see many mot inspectors being familiar with the wide variety of 'ignition on' lamp displays on many models. think it would be difficult to spot the odd missing one on every occasion ( a 'beep' os a dead giveaway though)

There again, I may be wrong.

As regards a sympathetic tester, may I suggest a busy garage might be pushed to get the mot's through faster.

 

Just makes me yearn even more for the old days when it was easy to manipulate virtually everything on the car *sigh*

Edited March 31, 2013 by acecard

[SilverBeast]

To be honest if mine goes permanent and I can't find out which sensor it is with VCDS Lite then I will link out each wear sensor in turn (on the plug on the wing) as the most likely wire to have a problem will be the one from the pad to the inner wing.

 

[SilverBeast]

Well it came on again.  

I was pretty sure it wasn't Off Side Rear as I only had those changed recently.

I managed to get at Near Side Front connector (the one on the hub) with the steering on left lock and connector seemed a bit flexible.

Disconnected it and contacts looked a bit corroded.

Reconnected and warning was gone wiggled connection and came back on.

Disconnected again and the whole shell of the connector attached to the pads came off leaving the two contacts behind!

 

Took off wheel so I could get at it more easily and cleaned up and superglued connector back together after cleaning contacts. Harness connector will not lock onto pad connector as the moisture seal at the back of it is a tight fit is probably dirty from not being fitted properly to broken connector.  Not too bothered as it is OK again now and the broken connector will get replaced when I do the front pads next time.

 

Pretty sure there isn't a sensor on the Off Side front as wiring on NSF is a Y lead shared with ABS sensor and couldn't see any wires on OSF (with wheel on).

[BigDog]

My brake pad warning lamp went on permanently. I changed the rear discs and pads today.  As many have said, only the offside rear has the wear sensing wire.  A pic of the new and old pads is attached if anyone else is interested.  The wire is not embedded in the pad as I had initially imagined based on previous cars, but instead in a moulding that is attached to the pad anti-rattle spring.  This gets cut through by the edge of the disc eventually.  It is still a bit of a mystery to my why it was intermittent at first.

 

Winding back the caliper pistons, I slackened the bleed nipples and caught the hydraulic fluid as others have said it's best not to force the fluid back through the ABS etc. I put Plastilube on the various sliding bits as it was recommended to me instead of copper grease.  All seems OK, the lamp is out, so the wiring is good after all. :)

 

 

Many thanks for the advice all.

Matt

 

[samconno]

I had the brake wear light come on just before my MOT. I just twisted the two wires together on the rear offside pads and inserted the wires into the existing hole and the light disappeared. MOT passed with no warning lights.  Have since replaced rear pads as they needed doing. Maybe a quick fix that could help somebody get through the MOT warning light failure these days.