89 W100 truck keep losing alternator charge

Truck alternator keeps failing/blowing. Just replaced with a 90 amp unit stock. Something in charging system is failing as truck will only run on battery power then die. Where is the voltage regulator on this truck? I cannot find it anywhere on firewall or what does it look like? What else could be doing this? Not charging at battery terminals. Not getting the 13 or 14 volts at battery terminal when meausured with volt meter.

Where is voltage regulator and what does it look like? is it square box?

Thnks,

Wizard

Regulator might be a part of the sbec(computer), located behind drivers headlight.

Okay, do you know if Autobone sells these new or if you can get one? Probably not if its a computer. Possibly a junk yard I guess? will call and check

Wizard

Called Autobone. They sell a computer for $188.00 other then that person I talked to knows nothing about what it does. They still tried to sell me the $18.00 bolt on voltage regulator that is no where to be found on truck that I can find

I only had an issue 15 years ago with my 90 ramcharger setting a diode switching circuit code but alt was still charging battery. Even then, the dealer sourced computer I got was a reman.

No voltage at battery terminal right now. Alternator not charging. Dad took it to a repair shop this morning. Did not want him to do this but I am at work and he only trying to help fix. Told him to stop as shop will be costly. I am with you, believe computer is problem. I called Autobone and Autozone. both can get computers for around $160.00 I can go to junk yard and probably get one for $10.00 from guy I know and take the chance. Also Autozne said they would take back the fried alternator now at no charge and give me a replacement. Question I did ask autobone is that computer specific to that year? They don't know and they said they do not see a spread of years that computer will cover. They did say you can use a D or B model (truck or van) for the same year. If I go to junk yard and pull one out of a 87 truck will it work or are things different?

Shop that my dad took truck to found problem. They said looks like mice were knawing at wires going into computer. They repaired wires and said truck is working fine. Will check everything once I get to it to see what they did and double check everything in working order. $75.00 bill included delivery of truck to my dads house after shop drove my dad back about 3 miles to his house one way.

Glad you got it sorted out.
Sounds like a good shop.
Be grateful.