Jeep XJ not charging

[benXJ]

So I put a 1998 4.0/AX15 out of a cherokee into my CJ. All was good, it was running fine for about 2 weeks, then one random morning I noticed a slight misfire as it was idling. I tested battery voltage and saw 10 volts. That explained the misfire. I shut the engine down to look around, all looked ok, no odd noises. I assumed bad alternator. I had to jump the jeep to get it back running and leave the jumper cables hooked up....tested voltage out of the back of the alternator and got 11-8 to 12 volts. Should be close to 14. So I replaced the alternator and got the same results. Then I temporarily grounded one of the voltage regulator studs and the volts spiked to 16. I believe this is telling me the alternator is OK and capable of putting out the voltage needed. I have spliced in a resistor on the battery temperature switch wiring. The alternator is controlled by the ECU. Has anyone dealt with that circuit failing?

My engine computer is from a 5 speed, but they are bit harder to find and are more $$$. I've read that an auto computer will work too, only have to bypass the NSS circuit.

Does this sound like the ECU is bad? Is there a way to bypass that and add an external regulator? Does anyone have a 1997 or 1998 XJ engine computer laying around that I could test with?

Thanks

 

[a_kelley]

You can add an external regulator. Yes the regulator is in the ecu. The auto ecu should work, just throw codes for the auto not being there.

 

[benXJ]

Thanks

But disregard. It helps to have all the wires connected.

Charging at 14.3 volts now.

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