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Did I just blow out my truck's alternator jumping the battery?

Hey there-- I just did something dumb. I had a dead battery on my '97 power stroke Ford F250. I realize now that when I was jumping it (successfully) I clipped the (black) ground cable to the alternator itself! Doy. The alternator is definitely dead now as I lose power after a few minutes of running the engine. My question is: did I blow a simple fuse or do I need to replace the whole alternator? How likely is it that I did further damage? I ask because I’m contemplating replacing the alternator myself. But maybe it would be wiser to get a tow to the mechanic. I thank anyone who can help me demystify my own rank stupidity.

Just how old is your battery . . . ?!

If you have a bad battery, your alternator does not stand a chance of doing its job properly

The battery is pretty new… I killed it by leaving a light on overnight.

Clipping the ground side of the jumper cables directly to the alternator body should not have hurt anything. But if that ground clamp touched the B+ post on the back of the alternator you may have damaged something.

Either the alternator, the battery, or the charge cable may have been damaged.

The charge cable is a fusible link, so keep that in mind as you diagnose this.

I would charge the battery on a charger for 6 hours.
Then start the engine and measure the voltage at that B+ post on the alternator. It should be around 14 volts with the engine running. If it reads 14 volts…the alternator is fine.
Next I would check the voltage between the battery posts (not the cable clamps but the center of the posts themselves). If you do not get 14 volts but did on the B+ terminal of the alternator, then the charge cable is burned out.
You can buy the fusible links at any auto parts store.



Thank you so much Yosemite. I will report back in a few days about how it went.