low charging, battery dies, changed alternator same problem

[94explorer2x4]

Just wanted to post this up in case it can help someone. My 98 v8 was cranking slow, battery not charging, and the charge gauge was fluctuating. I grabbed an alternator off one of my other v8's and installed it. the charging was good and all was well. Two weeks later it starts doing it again but now it will run fine but once it is shut off it will need a jump every time. Keep in mind that I am a mechanic by trade so I just threw an extra battery in the back along with a jump box and drive it like that for the next month. Easy fixed!
One day the voltage gets so low while driving the explorer would stall when the headlights were turned on. I Pull over on the side of 395 in BFNW and pull out the DVOM like I should have done in the first place. battery running voltage just shy of 12.5v too low to properly charge. Voltage at alternator B+ 14.5v A simple voltage drop test across the battery cables shows I have a drop of two volts between the battery neg and engine block. I crawl under the explorer and find the ground stud at the block was loose. I took it all the way out and wire brushed it then re torqued now all is good. When I got home I checked the grounds on both my 96 v8's and they were both on the loose side.
Nate

 

[beepinX]

Nice write up man, good trouble shooting! Thanks for sharing