I have a 1998 explorer XLT with AWD 4.0l V6 (engine code E) with 4 doors. I bought it not too long ago knowing it was driven cross states then parked witch is when I bought it. It needed a new fuel pump to start so I replaced that and the fuel filter (the tank is in perfect condition) the whole truck is basically in mint condition. No mods and it's been excellently taken care of. Only two owners (the guy I bought it from and his grandfather) it now runs and drives flawlessly and I put in a brand new battery because it needed one. After I drove it around a bit to test it out the battery died. I noticed the battery light was in and the volt meter on the dash was very low the whole time. So I used my multimeter and sure enough the alternator wasn't charging. So I replaced it with a remanufactured one from O'Reilly's and still the same issue. The serpentine belt was old and stretched out and the belt tenchiner was completely shot so I replaced both of those with brand new ones, alternator is still only producing .22 volts and it's barely keeping the battery above 10 volts.ive hear reman alternators are usually crap so I bought a brand spanking new one from rock auto it even came with the testing paperwork ensuring the alternator is performing well. Plug everything in again and it's the same deal. Only this time it's making .34 volts and now it can't keep the battery above 10.77 and eventually it dies soon after. (I'm testing the alternator by putting the positive from the multimeter on the charge cable that goes to the battery and the negative on the body of the alternator) I've checked the battery ground and the engine block ground and both have no voltage drop at all. I've checked all the fuses too and none of them are tripped. The only other thing I can think of is the harness being bad but I don't see how a bad harness would make the readings straight from the alternator .34 volts

 

Do some more checks at the alternator wiring.

You should have a lightgreen/red wire going to the alternator. When you turn the key on, you should have 12v on this wire.

You should have a yellow/white wire to the alternator also. You should have 12v on this wire key off and key on.

You should have 12v on the large black orange at the alternator at all times, key on or off.

It would be worth it to check the ground again to the alternator. I do not know how you checked it, but if you put one lead on the alternator case, and the other meter lead on the battery negative, you should get 0 or very very low volts if the alternator has a good ground.

 

I will certainly check in the morning. Although the black wire you are talking about I assume is the red wire I have. That's the one that bolts on as opposed to plugging in

 

That is suspicious. The factory used a black/orange wire. But yes, that is the large output wire of the alternator.

 

Ok here's what I got. Also my mistake the wire is actually black.

 

Ok. 1st off, your battery is seriously dead. You should put it on a trickle charge overnight.

2nd, your large black wire should be hooked to the battery. With that reading, it is obviously not. That large battery wire at the alternator should have read the 9v battery voltage. The yellow wire also. I bet if you fix the large black wire, that will fix the yellow wire also.

Here is a diagram below. You can see the large black/orange at the alternator is connected to the battery via a mega fuse. I bet that mega fuse is blown out.

 

Thank you indeed for your help. It was indeed the fuse🤦 experience learned I guess