99 xj sport.starts right up rev It up to 2k rpms battery starts a shooting up fast let go of the gas battery goes down to normal charge.then slowly will almost go all the way up causing an overcharge to the battery.tested the alt and alt is fine.also tested where u start it disconnect the one terminal on battery if it stays on means alt is doing its job.if not then its a bad alt.regulator is internal on the alt.so its gotta be regulator correct ?

 

Don't pull a battery cable off with the engine running. That practice can cause a huge volt spike and kill the ECM. The voltage regulator in in the ECM, not the alternator.

 

On a 99 its on the ecm? My dads been working on cars for 30 years he did that trick not me.and it was fine. Thought it was in the alt

 

Also the previous owner re did some wiring no extra wirinf just looked like he spliced into it amd hooked up a msd box I think it caused the regulator to get fried.the msd box is taking out. Now theses are the wires for the alternator the tape was takin off obviously I didnt do that wiring last guy did.can I get a whole new wiring harness and take that out and is that a pain.I cant find a good pic of what it looks like.

also It doesn't over charge when its idling and when u turn the headlights on the voltage goes down a bit then rev it and the meter starts shooting up but then goes back down. Weird

 

Don't you already have a thread for this very same topic?

 

I've had this this when I had a bogus battery.

 

Im on the second battery so its not the battery and it is a bosch battery.pretty sure its the regulator and wiring.ill just have to troubleshoot.the alt tested fine so what else would it be its gotta be the regulator and pour wiring.

 

Yeah about overcharging wanted to hear more thoughts on the regulator.I gotta get this on the road.

 

Do you have an FSM? Time to get off the computer and start tracing wiring diagrams. You'll have to figure out everything that has been re-engineered and fix it. BTW, wire nuts are usually used inside an enclosure in home wiring. Solder & heat shrink are the best way to go.

 

Yeah the dude did that.I know nothing with wiring or wiring diagrams.I have a haynes repair book.I cant even find in the book that the regulator is in the pcm.cause I think thats what it is.or could it just be wiring.I also dont know how to solder and heat shrink.the guy had ansd ignition box spliced into that wiring which is why it looks that way.now can I just take that wiring harness off get a new wiring harness and be done.cause I know where it leads too.

 

Heres more pics I was thinking if replacing that whole wiring harness but theres another wire its attached too then goes down next to where the head is