Alternator ??? help
Thread Starter
Racer
Joined: Apr 2006
Posts: 300
Likes: 0
From: OKlahoma City OK 89 vert
Alternator ??? help
At the alternator and battery has 15.20 volts when running. The dash shows 11.20 and the car runs sluggish. Is the built in regulator bad and not putting volt to the dash for a warning light to come on. What do I check or do next? Thanks Douglas
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Do you have a good working digital voltmeter ? 15.2V is to high. If this is correct, your voltage regulator diodes may have blown and the voltage is not being clamped properly.
As far as the 11.2V, this would be too low !!!!
I would first check Alternator and battery terminal connections.
As far as the 11.2V, this would be too low !!!!
I would first check Alternator and battery terminal connections.
Melting Slicks
Joined: May 2007
Posts: 2,171
Likes: 1
From: Warwick RI
Th first thing that I would check is your ground (-) to the block. It could be that simple if you haven't already. Clean it up and see if that made a difference in the voltmeter. If the car is starting when you leave it it may just be a dash problem as well. You would have trouble cranking long before it would run "sluggish" in my experience.
Thread Starter
Racer
Joined: Apr 2006
Posts: 300
Likes: 0
From: OKlahoma City OK 89 vert
Thanks guys
I went back and checked what you said. My digital voltmeter is more HI-TECH than I am. I had it sent wrong. After I put the battery charger on the battery. It would not start now. The volts are low, 11.20 with the car running. The same as the dash. I will take it in for a rebuild. Thank you guy.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
I went back and checked what you said. My digital voltmeter is more HI-TECH than I am. I had it sent wrong. After I put the battery charger on the battery. It would not start now. The volts are low, 11.20 with the car running. The same as the dash. I will take it in for a rebuild. Thank you guy.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Batteries are considered discharged at 12.0 volts and fully charged at 12.9 v or higher (max is 13.2 v). Normal alternator output is 14.7 volts cold and they drop to 13.7 volts hot. Dash voltmeters read 0.3 volts lower due to 0.3 volts drop across the ign sw contacts. 15.2 volts actually is within GM's tolerance for alternator output (max is 16 v). You should have seen the red battery symbol light on with the engine running at 11.2 volts.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Batteries are considered discharged at 12.0 volts and fully charged at 12.9 v or higher (max is 13.2 v). Normal alternator output is 14.7 volts cold and they drop to 13.7 volts hot. Dash voltmeters read 0.3 volts lower due to 0.3 volts drop across the ign sw contacts. 15.2 volts actually is within GM's tolerance for alternator output (max is 16 v). You should have seen the red battery symbol light on with the engine running at 11.2 volts.
Huh
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Nope, nothing in your C4 will be harmed by 16 volts across the battery. All the sensitive electronics has a voltage regulator supplying the electronics that can easily handle an input voltage of 16 volts.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Drifting
Joined: Jul 2007
Posts: 1,293
Likes: 36
Your battery self discharged like that? Make certain you don't just have a faulty battery with an internal short in it. If your alternator is putting out excessive voltage. . . and it is still not charging the battery. . . I would suspect the battery first, battery connections, and then alternator.
In any regard, whenever I've had an alternator issue, and the battery has some time on it (2+ years). I change BOTH and be done with it. A bad battery can overwork a new alternator and it won;t show up until a good time later when you will be replacing both.
Good luck with it!
In any regard, whenever I've had an alternator issue, and the battery has some time on it (2+ years). I change BOTH and be done with it. A bad battery can overwork a new alternator and it won;t show up until a good time later when you will be replacing both.
Good luck with it!