I am trying to judge the condition of the engine wiring harness on my car (94 E320 wagon), which I bought used about three years ago. There is no mention in the service record of a replacement of the harness, but that my not mean anything since nothing is mentioned in the record except for routine oil and filter changes.

I have cut through the cloth wrapping on the harness in eight or so places around the engine, particularly near the block, where, presumably, heat would be most likely to have caused the insulation to fail. Everything looks fine. And there is no sign of bad insulation where wires emerge from sheathing at connectors.

With one exception -- three wires at the back of the engine, right above the oil filter housing: one thickish wire with pink/mauve insulation, and two thinner ones that are brown. All three show the classic failure: insulation hardening, cracking, and falling off the conductor. The wires emerge from a black plastic outer cover, which is also pretty hard.

Can someone tell me if these three wires are part of the main engine harness -- and also what they do and where they go?

Any help much appreciated. pjbakewell