-How do you know that the VR is not working? What testing equipment did you use to come into conclusion-Did you check the dark green wire on back of the alty to the computer for an open or short circuit-Battery could be sulfated-Is it a 5.2L?

Informational links: https://www.2carpros.com/articles/how-to-check-a-car-battery
https://www.2carpros.com/articles/how-to-check-a-car-alternator

Hi rasmatz. I'm waiting anxiously for a reply. These voltage regulator circuits in the computers give extremely little trouble. The computers are all over the place in salvage yards but I'd be real surprised if it solves the problem, whatever it is.

I have Grounded the Green wire (pin 20) on the computer and after grounding the alternator kicked on. the head lights got brighter and the battery volts jump up to around 15v. I came across a similar problem on this site and after reading the response i tested the green wire. right now the alternator doesn't charge the battery. The volts on the battery stays the same whether the truck is on or off. and it is a 5.2L.

I could have misunderstood the topic i was reading but from what i understood was if grounding the green wire at pin 20 and the headlights got brighter and alt kicked in, then its the ecm that has the issue.

You have it right, but first I'd check that terminal in the connector. Also measure the voltage on that green wire and let us know what it is with the engine running. The regulator circuit could be open but they give such little trouble that I'd want to check all the other possibilities first.