Can someone please tell me exactly what the failure mode(s) of these harnesses are? What's specifically goes wrong with them -- does the insulation on the wires get brittle with age and crack, or does the insulation get worn away from particular areas due to mechanical interference or vibration? Or do the end connectors fail either physically or by corrosion? Or what else???.

Also, what are the components that the failure prone harnesses connect to? Is there only one harness which connects to ALL the electrical devices on the engine? Or is there a separate harness that controls the electronic fuel injectors, a different one for sensors and/or alternator connections etc.?

The reason I am asking is that I am just now starting a hunt for a clean 94 or 95 E class, and I would like to know what to look for both physically as well as symptomatically.

Sorry for the seemingly inane questions, but like I said I really am flying blind and am in need of some basic information. Thanks in advance for your help!

RTH