Brake pad wear sensors

[ChrisHC]

Continuing the discussion which started under the title 'Couple of electrical gremlins' -

Brian kindly provided a list of items that could cause a false warning from these sensors, the only one I had not tried was the multi-plug under the rear seat. I had a look at that over the weekend, and it seemed in excellent condition assuming I got the correct plug, it was white with 9 pins, 8 in use with one coloured green/violet present on one side but not the other, however there was no sign that a wire had ever been present. I nevertheless squirted electrical contact cleaner over the shiny plugs and sockets. I though this had cured the problem as the light failed to come on when I reassembled everything and tried the car, but next time the problem reappeared.

So is there anything else to check, for instance is there a plug in the loom connecting to the front sensor? Would there be any point replacing the big resistor behind the dash cluster?

[Brianmoooore]

The sensor wires at the plug under the rear seat should be blue/white (other end at pin 21 of the blue instrument cluster plug, and blue/yellow or green/yellow (seen both). This wire runs back to the front in the loom along the LH sill, then up the duct to the fusebox, where it passes straight through, and out as part of the loom that runs along the LH inner wing. About six inches from the fusebox, there are two crimped joints taped inside the loom, where the rubber wire to the front LH pad sensor joins the PVC wires.
The rubber wires are yellow and blue/green. Th rubber blue/green joins to a PVC blue green, which goes back the same route through the fusebox and into the cabin, then along to pin 26 of the white instrument cluster plug.
The big resistor in the instrument cluster is of a low resistance, and is extremely unlikely to fail, although its soldered joints are guaranteed to fail at some point, and will need to be resoldered.
Green/violet is the fuel pump feed. Does your car have the fuel pump some place other than inside the fuel tank?

[ChrisHC]

I do not think my fuel pump is anywhere other than the tank, so that is strange. I have been trying to post a photo of the connector without success, but it is probably not necessary. Your description of the cable run from the sensor gives me a thought, my car suffered from a mass of burnt out wiring behind the glovebox which DanThe sorted out for me and I remember that he said he had to go as far as the loom running along the LH sill. As you say the wiring from the sensor runs along that path, it may be that the cable is damaged and gives rise to an intermittent fault as a result, does that seem feasible?

[Brianmoooore]

Both wires to the rear sensor run along the LH sill, as do every other wire to the rear of the car - the loom along the RH sill is feeding from the back towards the front again.
Have you tried connecting a meter between the two relevant pins of the two instrument cluster plugs? You should get a very low resistance between the pins, and open circuit between the wire and the car's body.
May not be conclusive, of course, if the fault is intermittent.

[ChrisHC]

No, that is something else to try, thanks Brian.