So I have a 1996 Chevy Silverado and for the past 6 months my voltage had gotten pretty bad. It runs at about 9 volts constanlty. I have replaced the alternator and the battery and cleaned every ground I could find but still very low. Where should I start looking? Also, I dont know if this helps but the voltage slowly decreased over 6 months this didnt all just happen overnight.

 

I would start at both battery cables. There could be high resistance due to corrosion inside the cable and not easily seen.

 

Is the what the gauge shows, or did you actually check it?

 

Does your truck still start OK? If so, you don't really have low voltage (at least not at the starter). Use a meter to test at the battery then move "down the line" to ignition switch, alternator, etc 'till you find where you're losing voltage. Measure when under load (such as running the starter motor) or with headlights on bright. Don't believe the dash meter...