Pad wear light, need info...

[crashthecar]

I am looking to find out how the Brake pad wear circuit works.
Does the sensor just have to touch the rotor face to turn on the warning light or does it have to be worn through?

I ask this because my light is on but the Brakes on inspection are still appear to be proud of the sensor. (0.5mm)
Working on my bosses car awhile ago I found he had no sensors connected and no light on so I assumed that the sensor turns the light on when it is worn through and goes open circuit.

I disconnected both my sensors and checked but the light is still on.
Are sensors instantly stuffed when they touch a rotor or do they have to be cut through?
Is there any known faults with the curcuit or is there a way to reset the light that I don't know?

Any advice would be great.
Luke.

[Jeron]

On the E46 and probably E36 too, the light resets after a minute if you turn the car to on but don't start it.

The sensor has to wear through. If you want to go without sensors you need to close the circuit at the connection point or do what I do and just zip tie the sensor out of the way.

[crashthecar]

Update!
I got two new sensors from imparts this morning on the way home from work.
I disconnected the old ones and dummy fitted the new ones and hooked them up out of the way.
Bris BMW said the same as you, that to clear the light you fit the new sensors and turn the ignition on, leave it on for 30seconds or more then switch it off then back on and the light should have cleared.
No dice... light is still on with two new sensors. So i checked and cleaned the connectors and checked continuity of the new sensors, found them to be good.
Refitted the sensors and retested no change. As I said above the Bently has not got the pad indicator wiring diagram so I am now going to go back out there and go for a check back along the loom to check for damage...

I'll keep you posted...
Luke.

[Jeron]

I start with confirming that the light that is on is in-fact the pad wear light. If so then is there anything else that could trigger it, I think the answer is no. Finally, I guess you'll have to trace the wires back and check continuity.

[crashthecar]

Found the problem...
Where the brake line and associated wiring come down through the chassis in the back corner of the engine bay, the steel brake line had shifted and was rubbing on the chassis.
It had worn away it's protective rubber sheath and in the process cut the ABS wiring and the pad indicator harness.
No visible damage to the brake line was evident luckily.

My car has no ABS so this was no porblem to fix, I just finessed (BENT) the brake line away from the body and patched the wiring harness back together!
Turned on the key and no more light!