Hello folks,

I have a '94 5.7 TBI Silverado I hope someone can help me with. The charging system doesn't want to stay above 10 volts at idle. I had the alternator rebuilt, and the guy who did the work showed me on the test bench that the rebuilt unit was working properly. The wiring between the alt and the battery and the junction block is all brand new, so is the battery. The battery warning lamp (little red light in the shape of a battery) does come on when I turn the key to "on" position, and does go out after I start the engine. The voltmeter on the dash does show 14.6 volts initially, and then within 30-45 seconds after engine start will quickly drop down to about 11 volts. I have verified the voltage at the alternator battery terminal to ground with my flukemeter. I checked all the fuses in the fuseblock, they are all fine. I checked voltage at the single black wire to the alternator and it shows about 12 volts and slowly dropping at idle when disconnected.

What could be causing this undercharging problem? I am quickly running out of ideas and hope someone has encountered this problem before and conquered it! Any suggestions are greatly appreciated.

Feelix

 

Did you ever resolve this problem, I’m going through my truck right now trying to hunt down this drain