Nah, mud won't kill em. When your whellin and the battery light comes on, -yep, your alternator took a hit. What you have to do is pull them, pull regulator, blow out the alternator and free up the brushes in the reg. Their stuck, little stone chips lock them up. Been there done that many times, - got pics of that fix as well. You'll fry the comp before you fry an OEM alternator totally.