When driving at highway speed I had the amp gauge show only 12 v charging. Stopped and checked it out on the side of the road but couldn't find anything wrong, all connections looked good. started up again and it worked all the way back home; 1 1/2 hr drive. It is a recently rebuilt alternator. I had it pro checked and it is working fine. what sensor tells the regulator in the PCM that the alternator needs to work.

Any other ideas or thoughts are welcome

 

ESS ( Engine speed sensor ), BUT, it also would kill the tachometer if it were the issue, along with OD, AC, and cruise.

 

The pcm tells the alternator to work. Its one of the only things you actually need the pcm for. But instead of a 200 to 700 pcm....you can wire in an old school chysler regulator for about 18$ in about 20 minutes. Its an easy test to see if you have a bad pcm...and if your wrong you can switch back to the pcm, and leave the regulator in....a couple spade connectors and you can wire in up in a few seconds if say you get an exhuast leak that cooks your pcm, while pulling thru the rockies at night....lol......yep it happens....

 

There should also be a battery temp sensor beneath the tray.