Need alternator help

[fuzzmancometh]

Rundown. Had alternator rebuilt cuz I had it outta the car, no issues before. After installing, ran it for a few months and then it began to overcharge at 19v over 3-3500 rpm. Kills all gauges, lights, trac control abs... etc. Motor still runs tho. Took it back to the alt place that rebuilt it. He spun it to hell and loaded it at 130 amps and it was at 14.7, worked fine. So far I've cleaned all grounds I can get to. The one I cant, on the drivers side of the block, seems really cruddy. Ran my own ground to the block with jumper cables, still when snapped to 3500 rpm, jumps to 19v. Took apart alt, cleaned brush contact area. Retried, still fubar. Is there anything I'm overlooking here?? Need some help, dont wanna burn the pcm, also dont wanna not drive it, the kenne bell doesn't like to just sit there. Thanks in advance guys/gals

 

[unity]

Very odd. I highly recommend you pick up another alternator to try. Even if you "rent" one from a parts place. You need to rule it out, I dont care what the shop said that rebuilt it. And look at the battery too. A bad battery with some internal short can cause an alternator to run into over voltage. Get it tested or swap to another if you really think the alternator is sound.

 

[fuzzmancometh]

Very odd. I highly recommend you pick up another alternator to try. Even if you "rent" one from a parts place. You need to rule it out, I dont care what the shop said that rebuilt it. And look at the battery too. A bad battery with some internal short can cause an alternator to run into over voltage. Get it tested or swap to another if you really think the alternator is sound.

Swapped a new battery, no change. I was testing it with the guy who rebuilt it. Watched the whole process... he spun it so fast it threw the belt, never went over 15v and was maxed at 130 amps... I'm probably just gonna try a new alt. Just not convinced it's the problem tho

 

[BILLBOATS]

Hi, If a new alt in the car shows still 19 vts, could be a fault of some ground or short in the car's charging . If new one charges normal. 14-vts , likely its the rebuilt. The test you did rules out the rebuilt alt being the problem area. Its something outside of the alternator.

 

[fuzzmancometh]

Well if anyone is interested I ran my own circuits involved in the alt system. Still no change. Gave the alt back to the rebuilder who then took it somewhere. He spun it excessively high I guess. It overcharged finally. What he found was the rotor had a section that centrifically was getting pulled towards the rectifier or some shit, grounding and full fielding it. He had never seen it before. Rebuilt it again, works great. Thanks for your input, hopefully this helps someone in the future!!

 

[unity]

So it was the alt. Had a feeling.


I learned long ago to never trust new parts 100%. I had a 1996 Mark VIII, before I swapped it to COP. I had a weird issue. The care was like new and so was most of the parts. I had practically rebuilt the thing. But under heavy load at higher speeds it would bog down hard, like every cylinder was missing. Or it felt like the engine went into full retard. Basically, tons of power until I hit a point, say to pass someone, and then BAM. Spend $600 at a Ford dealer trying to figure it out (they could not figure it out) - and I do ALL my own work, so it was frustrating. Fast forward to another Mark, a 1995. My 96 was getting an engine swap. I had a LONG drive so I figured maybe I will swap over those nice new coil packs and wires to make sure I got goo milage. The 95 suddenly had the same issue. What the? Well, turns out one of my brand new coil packs had gone bad. Put the old coil packs originally in the 95 back in, back to normal! So here I was not being able to figure out this issues. Even with forum input. We all ruled out the new coil packs of course. Form that day forward, if I have an issue I even now consider new part failure as a possibility.