multiple alternator replacements with the same result. After a week the customer has a dead battery and the alternator puts out insufficient voltage ~ 8-10v. Putting a fresh battery in will bring the output to 12.5v. Repalced the atlernator again and get back up to 13.8-14.2v where all of the customer's other trucks charge under the same conditions. Cannot figure out what is killing the alternators. We have replaced the relays in the fuse box and the fuses on the battery terminal. The engine does not spin faster or slower than others on site and the pulley sizes are the same. This unit will stall when the positive battery terminal is removed while all of the other units will continue running.