Brake pad warning light - problem

I have a Rover 75 2.0 CDT and the brakepad warning light does not extinguish The pads are new and the leads and connections to the pads are ok Any ideas re likely fault may be ?

Regards to all and TIA

Its not a dealer reset thing is it?

I'm not at all familiar with the Rover 75, but I'd guess that they use a similar system to what BMW use (not that I'm familiar with those either!!!). BMWs have sensors in the pads that must be replaced (unless you changed your pads before the sensor triggered).

I'm told that it isn't ... but I will check with main dealer Incidentally I was assuming that the circuit used the worn pad as a connection to earth but apparently it works the opposite way. i.e. A worn pad creates an open circuit

Hmm ... well that is something I had not even considered The light came on when I was working away from home ... Not sure if it was a fault or worn pads I dropped vehicle into ATS and they changed the pads and also the front discs (they were scaled) The light didn't extinguish and they suggested it was a faulty connection on the front pad - I have checked it and it seems ok

On my E39 BMW, after changing pads and sensors, you have to leave the ignition on without starting the engine for a few minutes to re-set the warning light. If you don't it will take several days - by adding up the times the ignition is on before starting to make up the couple of minutes.

Ah, ATS, that explains it! They did fit new sensors, didn't they? (wear sensors wear with the pads, and are not reusable.)

Take it back to them, let them sort it.

If it's the same as BMW you have a sort of electrical wire loop covered in plastic. This fits into a cutout in the pad, but is about the height of the minimum pad thickness. When the pad wears enough, the disc cuts through the plastic and earths the wire, latching the light on. The idea of the loop is that it forms part of the warning light 'hold off' circuit. Break the loop - by say not fitting a sensor - and the light will stay on.

It must work in a similar way on the Audi A6. When the front brake pads were changed the light stayed on until the following day.

I'm not familiar with the Rover, but the brake fluid level sensor is worth a look. A lot of cars use the same w/light for pads and fluid level.

JOhn

I've not had the opportunity to investigate but from what I have learnt so far it appears that there is a sensor fitted to the brake pad as a separate component . This sensor is wired in series with the rear brake pad sensor and then to earth. This must mean that the circuit is complete until the pad wears down and breaks the continuity. Is anyone able to confirm this ?

The sensors are *probably* wired in series and any short to earth or break in continuity will latch on the warning light. It's designed to stop just omitting a sensor to stop the warning working.