I have a 1991 Explorer that has a charging problem. I had a battery charger repaired at a local repair shop. I wanted to see if it worked, so I put it on the Explorer to check it out. There were no problems with the Explorer before I did this. The following day, I noticed that the battery light was lit on the dash and the gauge showed it was not charging. Even though I know the charger was connected correctly, I apparently did something to the alternator. My question is thios, is there a fuse or circuit breaker somewhere for the alternator? Thank You

Did you disconnect both battery cables, prior to using the charger? If not, you may have damaged the alternator or something else. Begin by checking all under hood and under dash fuses with a test light or multimeter.

No I didn't remove the battery cables. I'm afraid that I did damage the alternator but not sure how. I have never removed the cables before when ever I had a dead battery on anything. I was just looking for a quick fix like a fuse or something.

It's not even adviseable to jump start batteries on modern-day vehicles. You run the risk of a voltage spike frying your alternator, ECM, or other sensors.

I replaced alternastor and all is well.

I have a 93 explorer where I was sitting at stop light idleing and suddenly my volts gage started spiking back and forth and car started jerking and idle went down to like 4 or 500 while in drive. Any Ideas on what it may be I think alternator Ill test and see any other ideas?

Chicophi180, it definitely sounds like the alternator is the problem. All indications are that the voltage regulator/brush holder simply needs replacing. Very easy to do on Fords and much cheaper than buying a rebuilt alternator. My gut is that you may only need to replace the brushes, which have worn down too far and are bouncing.

Additionally, be sure to remove and fully charge the battery, prior to using your rebuilt or new alternator. Most auto parts stores will do this for free. Otherwise, it will over-stress the alternator and may burn it out.