1990 Cherokee/ 1995 engine
 

I bought a 1990 Cherokee Laredo 4x4 with a bad knock in engine. My mechanic said it was a rod busted so he dropped in a 1995 engine. Everything on the outside is 1990 model parts, only the block and head is 1995. The transmission bolted right up and run fine. The alternator gauge is always showing minus on the charge/discharge. The starter and alternator both tested ok. My battery which was 5 years old showed to be weak so I changed it out. Last night two different times the radio quit playing and right after that the jeep died. Put it in park and start right up. The battery wires have insulation knocked off in places. Change those out maybe? The different year engine would not cause this will it ? I am not very mechanically inclined.