The generator light came on on tuesday so i replaced the alternator. still so voltage. ordered a power control module thinking it is the external voltage regulator, installed it today, still so volts. the batteries tested good, and the new alt. is good. no loose wires or wires that are grounded anywhere. i drove the truck for a while and drained the batteries now. dealership says that they need to flash the computer????? any ideas. and i cleaned the batteries and terminals

 

Tach work? If not you need to look at the crank sensor and its wiring. Without the crank sensor signal the PCM will not energize the field in the alternator.

 

check the fuse in the Power Distribution Center. could have been a short in the alternator that blew it in the first place. The need to flash the computer shouldn't be related to the charging problems.

 

the tach works and there is no fuses that are blown. the battery charger is on the truck now and the batteries wont stay charged long enough to get the truck to start now

 

Ck for 12v & ground at the alt field terminals w/ eng running.I've seen a few where the wire breaks inside the insulation creating an open circuit-but outside looks fine.You can ck this by gently pulling on the wires-the broken wire insulation will stretch easily