Brown wire and brown w/red trace


Active member
I putting a new Autosparks main harness in my 1991 D110 w/200 tdi. I have a thick Brown wire with a smaller gauge brown w/red trace tied into it. This wire comes out of the group of wires that go to the ignition switch. Color coding chart says brown w/red trace is Compression ignition starting aid to switch. On my 1991 D90 that wire is not connected.

My questions are…what is compression ignition starting aid to switch? Should this be connected?