Getting ready to put in a battery disconnect that also disconnects the alternator charge can anyone tell me wich wire is the alt. positive in. I don't have a manual or test light. It's a 1995 Cherokee 4.0
Exactly. Disconnecting just the battery will cause high voltage spikes that can kill the computer. I once repaired a Ford EEC-IV engine computer for this exact reason. The guy had installed a cutoff switch as required for autocrossing, and it blew the computer the first time he tried it with the engine running. You want the feed from the alternator on the battery side of the kill switch, or even better you use two pole switch that disconnects both at the same time.
Remove the existing wire from the alternator and insulate it(it will be hot from the PDM) and secure it.
Replace that wire with an adequately sized wire from the alternator.
Connect both the alternator wire and the battery wire to the same pole on the battery cut off switch.
You could trace the wire from the alternator to the PDM and completely remove it/them at the PDM if you will not be using it again. On the other hand, I think the early XJ's had two 60 AMP fuses in the PDM. Pull the fuses in addition to removing the wire from the alternator. I am not sure what year this changed because my 1994 had the fuses but the 1996 do not. Someone here should be able to tell you what positions the fuses are in.