"BMW Z3 - Automatic Braking System (ABS) Speed Sensor Cable Details"

Ron Stultz

2 March 2013

Summary: the cable going to the ABS spend sensor is a center, insulated conductor, a bare cooper wire twisted around insulated and then a foil shield with foil in contact with bare wire.

Background:

BMW Z3, 1997, 50,000 miles.

Fire in garage burnt cable going to side marker and ABS sensor.

Wires for side marker easily replaced.

ABS cable a mystery in its construction and thus to repair.

The BMW Z3, 1997, uses variable reluctance (VR) sensor technology.

ABS cable:

The wiring harness ABS cable has 3 pins in the connector where it connects to the actual ABS sensor cable.

Stripping the wiring harness ABS cable, discovered a center, insulated conductor, a bare wire wrapped around it and a foil shield.

Since 3 pins in connector, this suggested: center conductor; bare wire and shield tied to third pin.

Research on foil shield indicated that in some cables foil is on the outside with Mylar on the inside and in other cases, the foil is on the inside and makes contact with a bare wire as foil very hard to connect directly to a connector pin.

Upon examination of the ABS wiring harness cable, foil was on the inside, thus making connection with the bare wire.

ABS cable repair:

As appeared that insulation burnt off center conductor or stripped off in stripping outer, burnt insulation, clipped bare wire, loosened bare wire off insulated cable and used liquid electric tape to coat insulated center conductor well to make sure it would not contact bare wire.

Let liquid electric tape dry for several hours.

As bare wire now clipped, had to find a piece of stranded wire to soldier between the 2 ends of the bare wire.

Wrapped bare wire around insulated center conductor and soldered short piece of bare stranded wire between 2 ends of bare wire.

Now using ordinary tinfoil in a 1 inch wide strip, beginning at one end of the cable, wrapped foil around the cable as tight as I could get it without tearing the foil such that foil in contact with bare wire.

Once foil around cable completely, used hand to squish foil even tighter onto cable.

Using electric tape, wrapped entire length of cable, twice.

Used small cable ties to tie cable from one end to the other with special attention where electric tape mated with good cable.