Help ! Charging System Problem!!
Thread Starter
Heel & Toe
Joined: Mar 2021
Posts: 19
Likes: 3
From: Algonac
Help ! Charging System Problem!!
Hey there new member, so id like to apologize before hand if im posting in the wrong forum (new to how this works). Anyways been having issues with my 2007 C6 Manual lately. When i accelerate up to 4000rpms, the voltage drops significantly to about 10 or 11v. Once the rpms drop it returns to normal 14 to 14.5.. It only does this at high rpms. I had both the battery and alternator checked out at autozone and both were stated to be fine. Though i have heard that alternator testing doesnt actually occur at higher rpms. Anyways, i figured its the alternator and alot of mechanic friends have stated the same. That its on its way out and failing. Anyways, it is an original alternator in the car, and i had it rebuilt last year due to the bearings going. Not sure if they replace any of the other guts when they do that. Fast forward, brought it into the shop to have a new GM alternator put in it. Now its not charging at all. Anyone have this issue before? Kinda stuck at the moment and not really looking forward to the money involved in tracing down an electrical system problem. SO if anyone has experienced any of this before, please let me know. Any tips, tricks, and advice is welcome. Thank you
Drifting
Joined: Oct 2013
Posts: 1,495
Likes: 154
From: Somewhere Near Bakersfield California
Yes.
Long shot but a lot of have had a problem like yours. Try to go under your car and make sure your starter selenoid nuts are tight. Loose cables can cause these things. Don't go too tight or you'll break the plastic selenoid on the starter (ask me how I know).
I suggest remove nuts and clean all contact points and if you can use new nuts (maybe nylon lock ones).
This may not fix your problem at all but just my 2 cents of help
Long shot but a lot of have had a problem like yours. Try to go under your car and make sure your starter selenoid nuts are tight. Loose cables can cause these things. Don't go too tight or you'll break the plastic selenoid on the starter (ask me how I know).
I suggest remove nuts and clean all contact points and if you can use new nuts (maybe nylon lock ones).
This may not fix your problem at all but just my 2 cents of help
Melting Slicks
Joined: Apr 2019
Posts: 2,505
Likes: 1,166
From: Northern Wisconsin
Maybe the tension spring in the belt tensioner is getting weak so that the belt is slipping at higher speeds. Put a wrench on the tensioner to get a feel for the tension in the spring. If the tensioner is OK, then maybe you need a new belt.
Thread Starter
Heel & Toe
Joined: Mar 2021
Posts: 19
Likes: 3
From: Algonac
Thanks for the replys. everyone. Checked out all the wiring from the starter, to alternator to battery. Everything is fine. Got the new alternator and it is charging now at the 14+. However, with that said, the new issue is its giving the service charging system warning on the dash. No associated codes or anything. Checked all wiring, checked all the fuses and the horn fuse. But still baffled. Not sure, but i read somewhere where the alternators for these years was different. That the automatic had a decoupler on it and the manual doesnt. Could the presence of a decoupler cause a service charging notification appear on the dash? I had this happen before when i bought an aftermarket alternator, with the service charge warning, despite good voltage. Hence, the reason i had the original rebuilt at the time. Im baffled, Brand new stock alternator, good Red top Optima battery and all wiring seems to be in great shape
Edit: Forgot to mention replaced the belt tensioner and belts last year when i replaced the Harmonic balancer/Dampener. So im thinking good chance not belt slippage. The service charge light is the new concern.
Edit: Forgot to mention replaced the belt tensioner and belts last year when i replaced the Harmonic balancer/Dampener. So im thinking good chance not belt slippage. The service charge light is the new concern.
Safety Car
Joined: Nov 2013
Posts: 3,564
Likes: 1,098
From: Ex DPRK, now just N of Medford, OR
System is a nightmare to accurately diagnose, and the FSM can lead you astray. There are many threads here on this topic, but search function blows.
Decoupler won't have any effect.
The regulator outputs a monitor frequency to the cluster, and it's different between a C5 and C6.
Might be different between C6 years as well, but I don't think it would be.
Low resting battery voltage might cause the warning. I suspect that is the case when I still get the occasional message on first startup after sitting.
When I clear the error, doesn't reappear.
Good luck, please let us know what you find!
Decoupler won't have any effect.
The regulator outputs a monitor frequency to the cluster, and it's different between a C5 and C6.
Might be different between C6 years as well, but I don't think it would be.
Low resting battery voltage might cause the warning. I suspect that is the case when I still get the occasional message on first startup after sitting.
When I clear the error, doesn't reappear.
Good luck, please let us know what you find!
Thread Starter
Heel & Toe
Joined: Mar 2021
Posts: 19
Likes: 3
From: Algonac
So the vette is still in the shop. Had the original alternator rebuilt. new belt tensioner put on and a new belt as well. Still get the service charge system and voltage drops of car get around 4000 rpms. Tested the alternator itself at 4000 rpms for nearly half an hour. Kicks out a good charge so alternator is working. Any thoughts on this? Just dont understand why voltage drops at high rpms.
Drifting
Joined: Oct 2013
Posts: 1,495
Likes: 154
From: Somewhere Near Bakersfield California
So the vette is still in the shop. Had the original alternator rebuilt. new belt tensioner put on and a new belt as well. Still get the service charge system and voltage drops of car get around 4000 rpms. Tested the alternator itself at 4000 rpms for nearly half an hour. Kicks out a good charge so alternator is working. Any thoughts on this? Just dont understand why voltage drops at high rpms.
Contrary to popular belief, I believe a lose balancer can cause these things. Many don't think so and I've been told otherwise on my own balancer thread. When I changed mine it fixed everything. I got a Powerbond.
if a wobbly balancer doesn't cause charging system problems on these vettes then why do underdrive pullies cause some probs? Why could a bad tensioner cause pros? Maybe just MAYBE a wobbly balancer can have something to do with it. It did with mine.
My vette is an 08 LS3 BTW so check if an LS2 uses a different PN in case you do this as well and use Powerbond.
Goodluck!!
Last edited by Jaime-Corvette; May 14, 2022 at 12:15 PM.
Thread Starter
Heel & Toe
Joined: Mar 2021
Posts: 19
Likes: 3
From: Algonac
Hey Jaime thanks for the response. I had the death wobble on the balancer last year and replaced it this past october with a Summit Racing blaancer.. Everything worked fine. I did visually inspect the balancer and dont see any wobble or anything moving like it shouldnt. (I kinda check it all the time now cause didnt want a repeat of the wobble). Im really banging my head against the wall on this charging issue. Im wondering if the windings in the rebuilt alternator are bad. Im not sure what they when they rebuild an alternator, I believe a standard bench rebuild invoves the brushes, bearings, diodes and regulator. But something is telling it to either shut off at the 3500 to 4000 rpm mark, or the alternator itself just isnt functioning at those rpms. When everything checks out ok, im at a loss of where to go next.
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Drifting
Joined: Oct 2013
Posts: 1,495
Likes: 154
From: Somewhere Near Bakersfield California
Hey Jaime thanks for the response. I had the death wobble on the balancer last year and replaced it this past october with a Summit Racing blaancer.. Everything worked fine. I did visually inspect the balancer and dont see any wobble or anything moving like it shouldnt. (I kinda check it all the time now cause didnt want a repeat of the wobble). Im really banging my head against the wall on this charging issue. Im wondering if the windings in the rebuilt alternator are bad. Im not sure what they when they rebuild an alternator, I believe a standard bench rebuild invoves the brushes, bearings, diodes and regulator. But something is telling it to either shut off at the 3500 to 4000 rpm mark, or the alternator itself just isnt functioning at those rpms. When everything checks out ok, im at a loss of where to go next.
Also, im kind of young and never heard of anyone rebuilt the alternator or starters for newer cars cause it's like not really ever done anymore.
I would have never gotten mine rebuilt or consider it if it went bad. Just buy a new one from the parts store. Give it a try. If you know how to work the serpentine belt, the alternator is only 2 bolts, a wire plug and a wire lug on the stud. Very easy
Thread Starter
Heel & Toe
Joined: Mar 2021
Posts: 19
Likes: 3
From: Algonac
Tried a brand new factory alternator and was having same issue. Threw everything new at it with the exception of battery. Im thinking it might be a bad battery. I had the battery load tested and it came back good but a lil low. Im wondering if a faulty cell or bad cell could cause this high rpm voltage drop phenomenon.
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,629
What spark plugs and spark plug wires?
Some of the after market ones do not have enough resistance/RF suppression/ do not block RF noise from the plugs back to the coils, and since the ECM is controlling the voltage on the alternator, enough RF noise back to to ecm from the coils, will cause the ecm to drop the output voltage on the alternator.
As for rebuilding the altternator, if slip rings are replace (new one pressed on and wires solder back on).
The entire rotor assembly need to check up in lathe, with backside in live end, so it surfaces can be trued with shaft tram. If not, too much in and out on it surface, and at high speeds, can knock the brushed too far back, to lose continuity with the slip rings as high RPM's.
https://www.corvetteforum.com/forums...nator-fix.html
As for refurbished alternator,and constant charging fault problem at all engine speeds, but alternator is bench testing fine, then wrong voltage regulator installed in unit. The C6 and the C5 units, are the same for the most part, but used different voltage regulators.
Some of the after market ones do not have enough resistance/RF suppression/ do not block RF noise from the plugs back to the coils, and since the ECM is controlling the voltage on the alternator, enough RF noise back to to ecm from the coils, will cause the ecm to drop the output voltage on the alternator.
As for rebuilding the altternator, if slip rings are replace (new one pressed on and wires solder back on).
The entire rotor assembly need to check up in lathe, with backside in live end, so it surfaces can be trued with shaft tram. If not, too much in and out on it surface, and at high speeds, can knock the brushed too far back, to lose continuity with the slip rings as high RPM's.
https://www.corvetteforum.com/forums...nator-fix.html
As for refurbished alternator,and constant charging fault problem at all engine speeds, but alternator is bench testing fine, then wrong voltage regulator installed in unit. The C6 and the C5 units, are the same for the most part, but used different voltage regulators.