Tech Article Title Author Date
Porsche Brake Pad Wear Sensors for Stoptech Brakes Andrew Gray 2003

Stoptech's big brake upgrade for the S4 and A6 does not include the parts or instructions necessary to enable the "worn brake" indicator used by the stock brakes. Instead, Stoptech's installation instructions teach cutting the sensors from the pad and shorting the exposed wires in order to disable the worn brake indicator. As you will see from the instructions that follow, it is not difficult to modify the stock sensor plug harnesses to use Porsche brake pad wear sensors and retain the functionality of the stock worn brake indicator.

Given Stoptech's use of readily-available Porsche compatible brake pads, it occurred to me that Porsche brake pad wear sensors might solve this shortcoming of the Stoptech brake system. A search of the AudiWorld archives revealed Ming 2.7T's September 2002 post containing pictures of his Stoptech installation that show his use of Porsche brake pad wear sensors to enable the worn brake indicator in his A6.

 
As shown at right, after a relatively simple installation, the sensors work perfectly. The instructions below are designed to replace Step 13 in the Stoptech installation instructions (or Steps 10 and 11 in the APR Level 3 Brake Installation Manual).

Parts Needed:

  • 2 - Porsche Brake Pad Wear Sensors from a 1989-91 Porsche 928 - Part Number 928 612 365 01 - These can be purchased from any Porsche dealer (suggested retail is $18/each) or from The Tech Group in Northern California (650-610-0555) for $15/each (ask for Donna and tell her I sent you). A picture of the appropriate Porsche brake pad wear sensor is shown at right.
  • 4 - 1" pieces of 1/16" Heat Shrink Tubing
  • 2 - 3" pieces of 1/4" Heat Shrink Tubing
  • Solder

 

Tools Needed:

  • Wire Cutters
  • Wire Stripper
  • Soldering Iron Lighter or Heat Gun

Step 13 Modify Brake Wear Sensor:

In order to enable the "Worn Brake" indicator light, the brake pad wear sensor from the stock sensor plug harness needs to be replaced with a Porsche brake pad wear sensor and re-installed.

Prepare Stock Sensor Plug Harnesses:

- Cut the stock sensors from the two stock pad wear sensor harnesses leaving approximately 1 " of both wires behind the plug on each harness, as shown at right. I refer to this piece as a "stock sensor plug harness" below.

- Discard the stock sensors (or leave them on the stock pads/calipers).

- Strip approximately inch off the outer insulation from each of the two stock sensor plug harnesses and 1/4 inch of insulation from each of the inner wires on the two stock sensor plug harnesses (four wires total). One of the stock sensor plug harnesses, with its insulation stripped is shown at right.

Prepare Porsche Wear Sensors:

- Cut the Porsche pad wear sensors from the two Porsche sensor plug harnesses leaving approximately 1 " of both wires behind the plug on each harness. The picture at right shows one harness after I had stripped the insulation. I refer to this piece as a "Porsche pad wear sensor" below.

- Discard the harnesses.

 - Strip approximately inch of the outer insulation from each of the two Porsche pad wear sensors and 1/4 inch of insulation from each of the inner wires on the two Porsche pad wear sensors (four wires total). One of the Porsche pad wear sensors with its insulation stripped is shown at right.

 

Create Custom Porsche/Audi Sensor Harness:

- Slip one piece of 1/16" heat shrink tubing onto each of the inner wires on the Porsche pad wear sensors (four wires total).

- Slip one piece of 1/4" heat shrink tubing onto each of the two stock sensor plug harnesses.

- Solder the wires on the stock sensor plug harness onto the wires on the Porsche pad wear sensors (four wires total). It does not appear to matter which wire is soldered to which.

- Slide the 1/16" heat shrink tubing over the soldered connections on each of the four soldered wires such that there is no exposed wire that could short, and melt the heat shrink tubing into place.

- Slide the 1/4" heat shrink tubing over the previously heat shrunk wires on each harness and melt into place to seal the entire length of wires with the heat shrink tubing. A picture of the completed harness, which I refer to as the "Porsche/Audi Sensor Harness" below is shown at right.

Install The Custom Porsche/Audi Sensor Harnesses:

- Plug the Audi end of each Porsche/Audi Sensor Harness into the mating connectors on the car's wiring harness and dress the sensor wire to the brake line using the supplied high temperature ty-wraps (see Step 2 above (or Step 9 in APR Manual)).

 

- Plug the Porsche pad wear sensors into both brake pads on both sides of the car as shown at right.