Having an Issue with my 88 Formula, Battery is new and Tested, New alternator, tested as well. Volt gauge always reads below 8, and the battery will die if i drive it more than 10 minutes. Anyone know what next steps may be. Car had set for many years, but ran when I parked it while in service before I could get it painted and interior redone. Never did remove the engine. So at a loss right now.

 

Check the voltage directly at the alternator output.
If it's not there, you got a defective alternator...

 

I took it yesterday and had it bench tested, and it checked good on everything.

 

Unscrew and reinstall any all ground wires that you can see under the hood. When you unscrew the ground wire located near the battery ( the smaller wire coming off the negative battery cable ) be sure to clean it really good before screwing it back to the body. Do the same thing for the braided ground strap that attaches to the firewall near the distributor.

 

try adding a ground strap from engine block to chassis. On my '84 Trans AM, I had the alternator rebuilt & rebuilder repainted the alternator.
The alt would get so hot that voltage would then drop several volts.
There then was no ground between & the alt. Decided to try the extra ground strap like what I had to do on my 1972 Buick GS. Worked.