I highly recommend a higher amp rated alternator if you do replace yours. If it is a stock alt its probably 60-70 amps, and a 135 will slide right in and do a better job overall for you. I replaced mine with one from www.4alterstart.com
, and used their solid cased aluminum heat resistant starter. I have been very satisfied with both items for quite some time.
I would agree that unless you have a loose connection, your voltage reg is shot, and you should replace the alt at the same time.
Heat kills our alts and starters under that doghouse.