Is your plane old Continental six cylinder model, or newer Lycoming four??
Most propably it is wiring problem as mentioned above, if you have ALT and ALT fiels c/b:s separately which one pops?
Common point for wire chafing is just behind alt, and/or where they go thru front baffle. (Lycoming. Continental alt is installed to rear of the engine if it is old O-300) Bad clamping around eng compartment is very common as well, wire chafing to clamps because rubber cushionings worns away.
Sometimes wiring harness drooping just littlebit too close to exhaust risers...
