Brake pad wear warning system: Troubleshooting

[DaveMcKenz]

Good morning and Happy New Year.
I have been working in the Brake warning light system on my 84. There are three warning modes: Parking brake, fluid level and pad wear. My first two work fine. The brake pad wear light stays lit. At first I found missing sensors in front, so I hoped replacing them would fix problem. However with new sensors all around still have pad wear light always on.
Any ideas on finding either break or short in system? Any other suggestions?
I know I could just disconnect the bulb as a last resort.
Thanks,
Dave

[Drisump]

I'd check the quality of the connection where the sensor plugs into the harness. It would only take one funky connection to throw a persistant light. Cheers

[Bill Verburg]

Originally Posted by DaveMcKenz

Good morning and Happy New Year.
I have been working in the Brake warning light system on my 84. There are three warning modes: Parking brake, fluid level and pad wear. My first two work fine. The brake pad wear light stays lit. At first I found missing sensors in front, so I hoped replacing them would fix problem. However with new sensors all around still have pad wear light always on.
Any ideas on finding either break or short in system? Any other suggestions?
I know I could just disconnect the bulb as a last resort.
Thanks,
Dave

The pad wear sensor circuit depends on a series connection through the system, any break any where in the circuit will turn the light on.

[hangar21]

Dave,
Happy new year! I had similar problem in my 87. I decided to "close" each wheel circuit by installing temporary wires. This completed each circuit, but didn't turn off my light. Working with multi meter, I was able to eliminate each wheel circuit (independently), I finally found the short in the wire (rt. Front wheel area) & spliced in a new section of wire. In retrospect, I could have found the short with a "continuity" check, i didn't have to close each wheel circuit. But I didn't know that until after I had wired each wheel sensor closed. Hope this helps, good luck.
Terry

[DaveMcKenz]

Originally Posted by hangar21

Dave,
Happy new year! I had similar problem in my 87. I decided to "close" each wheel circuit by installing temporary wires. This completed each circuit, but didn't turn off my light. Working with multi meter, I was able to eliminate each wheel circuit (independently), I finally found the short in the wire (rt. Front wheel area) & spliced in a new section of wire. In retrospect, I could have found the short with a "continuity" check, i didn't have to close each wheel circuit. But I didn't know that until after I had wired each wheel sensor closed. Hope this helps, good luck.
Terry

Thanks, Terry,
I do indeed have a short to ground somewhere. I don't know where the wires disappear to once they leave the wheel wells. Where did you go to trace them?
Dave

[DaveMcKenz]

Well, I have an extra warning light assembly without a lens. I took it apart and soldered a jumper between pins 1 and 2, then put the board into my good warning light. The jumper fools the unit into thinking the brake pads are OK, and it behaves normally. Both lights come on with the ignition, then both extinguish when the engine starts.
I don't really like cover up solutions, but for now I have parking brake and brake fluid warning, and the other light won't be shining in my face, until I get things fixed better.
Thanks,
Dave

[hangar21]

Dave, I apologize for not taking any photos of that process. i finally found the short during a suspension rebuild(ER street/track2). During that process I had to remove the fuel tank, I also replaced all the A/C components. So the trunk area was wide open!
Additionally, my fuse block bar was cracked, PO had used a wrap ty to hold fuse in place( sorry, no pix of that either). I remember chasing the break was real PITA! Sorry I didn't really answer your question & I don't have my Bentley manual to reference the wiring schematic.
Terry

[DaveMcKenz]

Thanks, Terry. Your description makes me feel better about my current cosmetic fix. Someday when I have the front area torn apart, I'll look into the problem further.
Dave