2000 NBS Tahoe battery overcharging

[Trump]

2000 Tahoe LT 5.3 4x4 w/rear ac. In the past year, my headlights would dim for a few seconds during highway use. I replaced the battery that was warrantied (Wal-Mart). A friend was messing around with his new battery load tester and my replacement battery failed the test. I brought that battery back to Sears (die hard Platinum) and again i got a battery under warranty. Now my battery is charging at 15 volts. If i get the RPM,s over 3,000 the gauge drops to around 9 volts and the lights dim. Thoughts?

 

[oldchev]

Could be voltage regulator (integrated with alternator). Could be burned brushes or burnt slip ring in alternator.
There are places like auto zone that will check alternator on bench. Their machines are either on or off and don't have rpm tests. Many possibilities, but that's where I'd start. Alternators usually charge at around 14.1 volts or so. How are you checking the voltage?

 

[clandr1]

Could be voltage regulator (integrated with alternator). Could be burned brushes or burnt slip ring in alternator.
There are places like auto zone that will check alternator on bench. Their machines are either on or off and don't have rpm tests. Many possibilities, but that's where I'd start. Alternators usually charge at around 14.1 volts or so. How are you checking the voltage?

This was my guess too. Bad voltage regulator in the alt.

 

[Trump]

Thats not so bad. I was thinking the 2000 also has the regulator in the body control module. That is not the case in the 2000?

 

[clandr1]

Thats not so bad. I was thinking the 2000 also has the regulator in the body control module. That is not the case in the 2000?

I'm not 100% sure, but I'm pretty sure that voltage regulators have been integrated into alternators since the late 1970s.