alternator/battery issues ford explorer
 

Hi, posting another thread, My son has a 2004 Ford Explorer, a few days a go the battery light came on ( still on) from checking it seemed like needed an alternator replaced that ( got three of them thought mabye first two were defective) still having issues. Here are main points;
replaced alternator ( re manufactured one)
battery is one year old ( bought at and installed by Ford dealer) this seems to be working ok
When truck sits overnight, it will start fine but only reading to the 1/2 way charge, when u put on heat or whatever it will drop slightly then go back up to 1/2 if you drive it, he watches it drop considerably and will die completely soon.
Battery, although think is fine, when we charge it up it only reading 12.86 not sure if it is something to do with alternator not working properly?
checked starter connections, seem fine
AT idle alternator is putting out 12.4V
Bought a multimeter to check fuses but not entirely sure how to go about or how to set them when trying to read each one.

Any suggestions we could try would be appreciated! Thanks:(

Look for bad connections ,
Check the voltage coming out of the back of the alternator. and at the battery see if its different.
Probe the battery cable and see if it has good voltage, but not getting to the battery .
Put jumper cable on the battery from another car while running and see how high the battery voltage will get.

Thanks, my nephew came over and checked those things you listed, told my son to find some wire that came out of battery and when they followed the wire they found out it was corroded so they stripped it and reconnected it. Fingers crossed he started the truck and the battery light went out! All seems to be well and saved us a ton of money. Thanks for the advice