13.8-14.5 normal 
Starting issues (PLEASE HELP)
Thread Starter
Pro
Joined: Jul 2011
Posts: 585
Likes: 12
From: Moore OK
So this morning I was in the garage about to take the alternator off to be tested. For whatever reason I decided to double check my wiring from last night. I knew I was tired but not tired enough to do what Im about to say (LOL I did work a full 8 hr shift and then played two back to back softball games). I guess when I was wiring the alternator pigtail I was looking at the plug backwards and wired it accordingly. I cant believe I did that! Needless to say I rewired the correct way and fixed the SCS issue. I am thrilled that this was the fix bc I was about to start tearing off the serpentine belt and alternator to get it tested. Car now holds a solid 13.8-14.4v on the guage inside and about 14.8 coming off the alternator. She should be back on the road in no time after I install the new Doug Rippie extended wheel studs for the new weld racing S77bs I just purchased. Thanks for all the replies/help!
Melting Slicks
Joined: Dec 2013
Posts: 2,232
Likes: 315
From: Bridgewater New Jersey
So this morning I was in the garage about to take the alternator off to be tested. For whatever reason I decided to double check my wiring from last night. I knew I was tired but not tired enough to do what Im about to say (LOL I did work a full 8 hr shift and then played two back to back softball games). I guess when I was wiring the alternator pigtail I was looking at the plug backwards and wired it accordingly. I cant believe I did that! Needless to say I rewired the correct way and fixed the SCS issue. I am thrilled that this was the fix bc I was about to start tearing off the serpentine belt and alternator to get it tested. Car now holds a solid 13.8-14.4v on the guage inside and about 14.8 coming off the alternator. She should be back on the road in no time after I install the new Doug Rippie extended wheel studs for the new weld racing S77bs I just purchased. Thanks for all the replies/help!
Thread Starter
Pro
Joined: Jul 2011
Posts: 585
Likes: 12
From: Moore OK
UPDATE:
Car was running fine holding great voltage 14.0 up to 14.8 after the new pigtail was installed right before my wife and I left for our anniversary weekend. Came back today and installed the new DR extended wheels studs. Got everything on and took the car for a drive (volts still good at this point). I get to the gas station about a mile away and the damn SCS light comes back on again. Im sure you could imagine my attitude at this point :-[ Next is going to be to remove the alternator and get it tested and possibly rebuilt just for a piece of mind. Im really getting tired of seeing this light on the dash. I just cant see how replacing the plug can fix the issue for an hour or so of running and then its craps out on me all the sudden. Im in a loss for words.
Car was running fine holding great voltage 14.0 up to 14.8 after the new pigtail was installed right before my wife and I left for our anniversary weekend. Came back today and installed the new DR extended wheels studs. Got everything on and took the car for a drive (volts still good at this point). I get to the gas station about a mile away and the damn SCS light comes back on again. Im sure you could imagine my attitude at this point :-[ Next is going to be to remove the alternator and get it tested and possibly rebuilt just for a piece of mind. Im really getting tired of seeing this light on the dash. I just cant see how replacing the plug can fix the issue for an hour or so of running and then its craps out on me all the sudden. Im in a loss for words.
Last edited by bp92gsr; Sep 1, 2014 at 08:11 PM.
Le Mans Master
Joined: Feb 2007
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From: Currently somewhere in IL,IN,KY,TN,MO,AR,MS,AL, or FL
So you connected the battery to an unused terminal, and swapped the turn on signal and the field duty cycle signal to the solid state voltage regulator. If the wiring is now good I would assume the regulator is toast but it could also be the Engine Control Module (ECM) that supplies these signals. Any new codes to narrow the possibilities?
Thread Starter
Pro
Joined: Jul 2011
Posts: 585
Likes: 12
From: Moore OK
So you connected the battery to an unused terminal, and swapped the turn on signal and the field duty cycle signal to the solid state voltage regulator. If the wiring is now good I would assume the regulator is toast but it could also be the Engine Control Module (ECM) that supplies these signals. Any new codes to narrow the possibilities?
Le Mans Master
Joined: Feb 2007
Posts: 8,514
Likes: 235
From: Currently somewhere in IL,IN,KY,TN,MO,AR,MS,AL, or FL
My first sentence describes what you did when you wired the alternator connector backward. This isn't a '53 Buick. The alternator controller built into the alternator is a solid state device that has a digital signal to turn it on and off and a pulsed AC signal that controls the output. There is no voltage regulator in these cars as such. The ECM measures the battery voltage as one of its many functions and turns the alternator on and off and also sends pulses that the alternator controller uses to produce the required output. With this arrangement the ECM is able to control not only the battery charging but also the load on the engine.
Swapping wires exchanged the AC voltage from the ECM which is actually measuring the battery voltage and trying to control the output (the equivalent function of a voltage regulator) with the ECM's alternator on/off terminal.
It sounds to me like you just released the magic smoke from the alternator controller and not the ECM.
Swapping wires exchanged the AC voltage from the ECM which is actually measuring the battery voltage and trying to control the output (the equivalent function of a voltage regulator) with the ECM's alternator on/off terminal.
It sounds to me like you just released the magic smoke from the alternator controller and not the ECM.
Melting Slicks
Joined: Dec 2013
Posts: 2,232
Likes: 315
From: Bridgewater New Jersey
Here's a interested thread to read, Service Charging System issues.
https://www.corvetteforum.com/forums...ng-system.html
Something to keep in mind.
https://www.corvetteforum.com/forums...ng-system.html
Something to keep in mind.
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Le Mans Master
Joined: Feb 2007
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From: Currently somewhere in IL,IN,KY,TN,MO,AR,MS,AL, or FL
In the linked thread there are a lot of posts about the issue being the horns. Yes, the ECM appears to use the voltage down from the horn fuse to determine how to control the alternator. That is where the "battery" connection at pin A on the alternator goes. More proof this isn't a '53 Buick with a simple voltage regulator with mechanical solenoids that pull in dropping the charge when the voltage or current get too high.
Thread Starter
Pro
Joined: Jul 2011
Posts: 585
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From: Moore OK
Car is for sure fixed
Got the alternator back from the shop and they troubleshot it down to being the voltage regulator. Put a new one on for $70 and reinstalled on the car. Immediate change in how quickly the car started and runs strong. For anyone following this thread who gave input, THANK YOU! Just did a massive cleaning and detail after I broke in the new brakes and pads with the new wheels and tires. Love this car again.
