Grounds all looked good. Any idea's for my next culprit to look at??

 

Got to be a bad alternator again!


Inside of the alternator is a regulator, that regulator isn't stoping the over production of volts when AC is convered to DC current (which is about 18-19 volts becuase of the amperage). You ensured this by measuring the voltage at the battery with a second tester and had the same results during the problematic occurance. Over production is a alternator issue, the PCM only tells the rectifier bridge to turn on and the alternator produces DC current. There are usually 4 ways a alternator goes out;

1. Bearings
2. Brushes and that leads to low or no voltage
3. Over production
4. A bad battery or arching of wires/connections

Also you can check the other ends of the battery cables at the lugs and ensure that (for instance) the ground to block is clean and tight.

 

Alright....I'm on alternator number 3 now. Same results each time: voltmeter starts off dead center, then slowly climbs to high range, then snaps over fully right into the red. Reads 18+ volts at battery.

WTH??

 

If you have went out and tested 18 volts at the battery when the gauge states 18+ volts then you have nailed it down to overage output. At this point I don't know what to tell you. It makes absolutely NO sense. Take it in to a shop at this point.

Please update us when you get this fixed.

 

Alright.....finally, FINALLY, got it sorted. And in the process I believe I stumbled across the best Mobile Maintenance guys out there.

Turned out the culprit for all the overcharging issues I was having was a short of some sort happening in the harness.

After an hour of taking voltage readings across everything known to man under the hood, and nothing making any sense, we discovered that the voltage change going to the alternator plug (green wire) would increase when a section of the harness was moved.

An hour later, the overlay wire was spliced in....going from the back of the alternator plug over to the corresponding pin on the PCM.

Maybe not the optimum solution, but it's now fixed and back on the road.

 

I bet you had a pretty nice light show at night with the lights out under the hood! LOL

 

can you tell me what pin # on the pcm

 

This also could be a bad battery sensor issue, which is a sensor located under the battery and controls voltage that the alternator outputs. I would just replace it as well.