how to reset brake light

Sat Jul 21, 2012 5:23 pm

iv changed my brake pads, discs and put in new sensors but the brake lining light stays on.

how do i rest the light?

Sat Jul 21, 2012 5:28 pm

Does your car have discs at the rear?

Sat Jul 21, 2012 6:05 pm

daimlerman wrote:Does your car have discs at the rear?

yes ii does, but none ABS

Sat Jul 21, 2012 6:18 pm

I'm working on the asumption that you have swapped just front discs/pads/sensor,have you checked out the sensor on the rear brakes?

Very simply,that's how the warning light circuit works,a live wire shorts to earth and the light comes on,so any place on the sensor wire's run where it can rub the insulation off and earth will put the light on.

when you have established that the wire is not rubbing in this way,the next most likely fault is within the main circuit printed board within the instrument cluster,just behind the temperature gauge there is a large resistor that can develop a dry joint....this usually gives a flickering light,rather than a steady 'on'.

Sat Jul 21, 2012 10:30 pm

Ive changed discs and pads front and rear with new sensors, and the light in the instrument cluster is always on, no flickering

Sat Jul 21, 2012 10:45 pm

Most likely the aforementioned dry joint. 3 of my clusters had this fault and the light was staying on rather than flickering. http://www.e30zone.net/e30zonewiki/inde ... ear_Sensor

Sat Jul 21, 2012 10:50 pm

The sensor circuit works as Daimlerman says, but not only as he says.
The light initially comes on when the sensor wire begins to short to earth (i.e. the metal of the disc), but stays on permanently when the sensor wire is broken, without any part of the wire being earthed. The loops of wire in both sensors are connected in series and used to pull the base of a transistor positive into a non conducting condition. The current in this loop is limited by a certain 220 ohm resistor.
When the wire is earthed or broken, another, larger value, resistor can pull the base negative, the transistor conducts, and the warning lamp lights.
If your light is still on after replacing both pad sensors, then a sensor plug/socket is not making contact properly, or the resistor is dry jointed (doesn't always result in a flickering light).
If the light went out initially, but came back on after a short amount of driving, the wires to one of the sensors weren't 'dressed' correctly, and have worn through on the inside of a wheel rim.

Sun Jul 22, 2012 3:05 am

I was thinking when I read the initial description and it reminded me of a similar fault which I traced to oxidised contacts in the plug and socket due to moisture.

Sat Apr 18, 2026 12:42 pm

I am dragging this post up from 2012 to ask if this fault, ie dim handbrake light on after letting the handbrake off. Will this fault also cause a battery drain issue which I have been unable to trace. Cheers in advance.

Sat Apr 18, 2026 1:56 pm

Doubtful that would cause any parasitic drain, since I think it only lights with the ignition switch on. Check your glovebox and boot lights actually go off when they're closed - you may have to remove bulbs to check this. Also a faulty glovebox torch can cause such issues...