Hi there, been trying to re-wire my jeep for a while now. Almost all done but I am stuck on the alternator. My jeep is an 1988 YJ with the 4.2, but I recently did the MPI conversion. Everything went pretty well, just time consuming. The jeep starts and runs, but the old alternator is still in place. It seems to be charging, but keeps kicking the check engine light on. I bought the 92-95 style alternator, but need some assistance on how to wire the thing. Any help would be appreciated. I read somewhere about the Dealership part # 56017763, but I'd rather now spend the $135. Thanks a lot
Originally Posted by demesauce View Post
I'm assuming that you have installed the 4.0 engine bay harness if you went through an "mpi conversion", and if so, all the wiring/connectors are there to correctly attach a "new style" alternator - this alternator needs the ECU to regulate the charging voltage.
What's the dealership part you mention in your post?
All of the error codes refer to the alternator. I have the ECM/wiring harness from the 4.0 jeep. And the error code is saying that the alternator is not talking to the ECM. The problem is the wiring harness is from the 4.0 but the alternator is from the 4.2. I need help wiring up my new 4.0 alternator to the rest of my 4.0 system.
I just went through this yesterday. If you have a 4.2 alt. then you should need to install a 7.5 amp diode on the feild wire from your new harness. If you have a 4.0 alt. then there should be 2 green wires on the back of it. One should have a black stripe. Im a little foggy on which one is which but one of them hooks to the alt. feild wire from your new harness the other gets hooked to a switched 12v source. The feild wire in my Hesco harness is blue.
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