Alternator Issues
Thread Starter
3rd Gear
Joined: Sep 2024
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Alternator Issues
I have a 1997 Corvette that has a 6.2L LS3 in it. For the past few months I've been having issues with my battery slowly dying when I drive for 20+ minutes. Originally I was getting the 110 amp alternator for the early C5's and I later switched to the 145 amp that the ls3 uses. Unfortunately, I still have the same issue where the voltage just dwindles down as I'm driving. Every time when I've initially put in the new alternator it'll keep the voltage at roughly 13-14 volts, but after a week or two of use, I'll end up slowly dying on my way to the house. I've checked the cables that run to the starter and the fuse is still good on the charging cable, and they're both clean/making good contact. Any recommendations? I'm gonna check the ground for it in the morning to see if that could be the issue.
Melting Slicks
Joined: Sep 2008
Posts: 3,101
Likes: 789
From: Espanola New Mexico
Have you actually measured voltage at the battery terminals while the car is running? One possibility is you have excessive current drain when the car is off like sitting overnight.
Burning Brakes
Joined: Nov 2013
Posts: 938
Likes: 297
The alternator ground thru its case to the bracket, to the motor. Make sure you have grounds from the motor to the frame/battery- if you think it's a ground issue
I had a ton of regulator failures on my Tahoe a couple years ago. The alternator shop that was helping me replace the regs suggested my battery was the cause. I had an AGM at the time. I can't explain why, but I went with a new flooded bath battery on the last rebuild and it's been good since
C5s have a couple different alternators, with the regulator being different manual to auto cars
Trouble shooting steps would be to test alternator output, verify battery isn't shorting when it gets hot and verify you have the proper regulator for your PCM to excite. I guess along those lines, make sure the PCM can excite the alt, or convert to a single wire alt excitation
I had a ton of regulator failures on my Tahoe a couple years ago. The alternator shop that was helping me replace the regs suggested my battery was the cause. I had an AGM at the time. I can't explain why, but I went with a new flooded bath battery on the last rebuild and it's been good since
C5s have a couple different alternators, with the regulator being different manual to auto cars
Trouble shooting steps would be to test alternator output, verify battery isn't shorting when it gets hot and verify you have the proper regulator for your PCM to excite. I guess along those lines, make sure the PCM can excite the alt, or convert to a single wire alt excitation
Tech Contributor
Joined: Jan 2007
Posts: 19,115
Likes: 1,038
From: Dyer, IN
I have a 1997 Corvette that has a 6.2L LS3 in it. For the past few months I've been having issues with my battery slowly dying when I drive for 20+ minutes. Originally I was getting the 110 amp alternator for the early C5's and I later switched to the 145 amp that the ls3 uses.
Thread Starter
3rd Gear
Joined: Sep 2024
Posts: 3
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Not a clear statement. Does this mean you purchased the correct alternator for your year car, installed it and it did not work.......Then you purchased an alternator for an LS3?
Measured where and by what method? DIC? IPC? DMM?
Was measured by DIC
Meaning what? Does the engine start to stall or is this just a voltage on the DIC that continues to drop?
Voltage Started dropping as I was driving
Using what method? Visual inspection? Have any measurements for voltage or ground been taken with a DMM?
Measured where and by what method? DIC? IPC? DMM?
Was measured by DIC
Meaning what? Does the engine start to stall or is this just a voltage on the DIC that continues to drop?
Voltage Started dropping as I was driving
Using what method? Visual inspection? Have any measurements for voltage or ground been taken with a DMM?
Ended up being, my starter went out and was causing all of my issues... no weak starts or weird voltage drops while driving anymore. Ran strong for my 45 minute drive, started right up after sitting for 10 minutes then made the drive back no issue.
Team Owner
Joined: Oct 1999
Posts: 31,975
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From: Guinness Its whats for B'fast JAWGA
CI 3-4-5-9 Veteran
Eric had some good posts on rebuilding his alternator. Corvettes can be picky on which alternators work. If the problem comes back, I'd try rebuilding the original if you still have it. Power runs through the starter and ignition switch dirty contacts can cause all sorts of odd problems.
https://www.corvetteforum.com/forums...-bearings.html
https://www.corvetteforum.com/forums...-bearings.html
