My GF took my truck to work and left the lights on all day. When she went to get jumped that afternoon the jumper cables were hooked up backwards. I assume that it is just a fusible link that was torched. Is there anything else I need to look for?

This is for a 1992 F-150 5.8l 4x4.

Thanks, Bryan.

 

Probabilities are real high the alternator is now toast and it will drain the battery over night. It'll test okay as the output is there but the final diode allows the current to drain back out of the battery when the key is off- kinda like a direct but controlled ground. Once you get it fired back up, test it by taking the large wire off of the battery with the key off. You're looking for a small amount of arching as you remove it. If you see it, it's toast. If you are replacing it, look for a new, not rebuilt unit. Most often the rebuilders do not test for the diodes being good and it's the most common failure on a Ford alternator. Remy makes a pretty good one. I just replaced the one on my 91 Bronco and it was just under a hundred bucks for new.

 

Yup, it is confirmed that my alternator is draining my batt. Thanks. I would have gone straight for a new battery.