before you go buy an alternator check your fuse

[Jenn&Amanda]

I have a 2000 explorer 4.0 OHV, my battery light came on last week, check the alternator and all signs pointed to my alternator. So went to the parts store, his machine was down so I bought the new part anyways (we just bought the truck) thought it wouldn't hurt. Well everything went well but stupid battery light was on. Went and had the whole charging system tested and was told everything looked good, maybe the battery just need to charge more. Do a little running around and I go to crank the truck and it acted like a cable loose. Checked all cables and connections everything was fine. Then I thought mmm, let me check the fuses, sure enough my voltage regulator fuse (30 amp). Jumped the truck off and it started perfectly. Battery light went off and has been running great ever since. ****to save some cash check your fuses first lol!!!****

 

[SoNic67]

Usually the fuses don't burn for no reason. They are very reliable devices due to low complexity, 99.999% of the time it was something else at fault if a fuse is blow.

 

[Jenn&Amanda]

So what could it have been though?

 

[SoNic67]

Bad alternator (internal regulator).
The fuse is installed there to protect the cable from catching fire when it is a short-circuit on that circuit.

Sure, it seems annoying that the fuses "blow", but it is better than an engine bay fire started by harness insulation melting and catching fire.
See below just a small portion of what happened to me because a Chinese fuse didn't blow correctly (the store recalled latter the fuse set):