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4wd Conversion Finished, Alternator wont charge?

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So i just completed my 4wd conversions on my 88 MJ. Went from 2wd, ba10/5 to 4wd, AW4, NP231. I had to swap the engine compartment harness along with my ECU. So the jeep got running on the 1st crank, but my alternator is not charging. Gauge reads at 10v and i checked with DVM and its 11.90 at posts and same thing when i checked at alternator post. I had a spare alternator (known good), and i swapped it and still the same. I'm not sure where to look now. I'm gonna check for any open wiring again, but i did a pretty good look and found nothing. Any ideas? I know my power cable to alt has battery voltage so the problem is with the regulator. Another thing is i have not yet bolted in/grounded my ECU... its just sitting there in the cab. Perhaps it needs to be grounded as ive heard regulator is in the PCM... I need some helps ASAP, can't wait to test drive this thing..


Any tips anyone?


Randy B.

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Double check your wiring at the starter relay, trace all the wires that should be hooked up from the FSM, or wiring diagram.


Yes, get your ECU grounded, even run a separate ground wire from the mounting plate to the ground stud on the engine block.


I'm surprised that you got it started with out the ECU being grounded :eek: I've had that problem before with the fuel pump not running because the ECU was not grounded.


And where did you get the PCM from :dunno: That's a Ford brain box.


Oh, and one more thing........is the belt tension set tight enough??? or is it slipping at the alternator???

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Hahah PCM, meant ECU. You knew what i meant. lol :doh:



Ok........as long as you don't start asking where the EEC connector is, we'll be just fine....... :roll:



You should have 3 wires coming off the alternator -


The 18 Tan line is for the dash warning light. "L" post on alt. connector.


The 16 Yellow feeds to the ignition module. "F" post on alt. connector.


And the 8 Red to the starter relay, alt. feed.


You have no mention of the #8 Red wire :dunno:


The book says..........Detach wired from alt. Switch on, engine not running , connect voltmeter from ground to "L" = zero reading indicates open circuit between terminal and battery. Correct as required.


That's about all there is to test, except for the run-test across battery post, getting within 13.0 volts or above for output.

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