Alternator Woes?
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Alternator Woes?
After a few years of chasing variable voltage readout (issues), I finally decided to have my CS130 rebuilt. Maybe it wasn't the best choice -- since it was pointed out that the subsequent CS144 has been used [possibly] more successfully. The reason I chose this route is because I polished the case a few years back...while have it rebuild "just for the heck of it". The real goal was to match the rest of the engine compartment polish.
Seeing voltage spikes to 17 volts is what finally prompted my decision that it HAD to be the alternator causing the readings ESPECIALLY when I also saw dash/headlights vary in brightness. Prior to the rebuild, it almost always slowly dropped from mid/upper 13 volts into the 12's...and even 11's. Only two times had I seen voltage variances translated into headlight variances. Otherwise, mostly the gauge readings were the issue. However, when voltages dropped into the mid/lower 11's it sometimes resulted in lacking of cranking to restart. Plus, it goes without saying, I had to put it on a charger a lot....when sitting for days....as it often did.
I've only driven it 5 or 6 times since the rebuild but anomalies persist. Since the rebuild, one thing SEEMS to indicate improved/stabilized performance. Voltage on the first two drives stayed stable around 13.8V. However, a few days later after a longer 1/2 hour drive), I saw the voltage (once again) drop to the mid/upper 11's. On the fourth/fifth drive, headlights dimmed/brightened during the first few seconds of start-up. Voltage rose from mid 11's back up the 13's after approx 10 mins. (I can't remember how many days it sat, but it wasn't more than a week and I'd charged the battery after re-installing the alternator.
If the battery HAD gotten that low (again), would it be possible to SEE voltage variations in the headlights IF THE ALTERNATOR WAS TRUELY REPAIRED?
FWIW, I replaced the battery within the last 2-3 years. Because the charging issues I've rarely driven it over 20 miles for fear of being stranded. That's why I finally decided to rebuild it again. Because of the two incidents (one where headlights fluctuated...and the other where voltage dropped after a longer drive), my worries of being stranded are back. Should I call the armature shop and alert them I still have problems...and that the rebuild might be "problematic"? Is there any connection point in the wiring where both problems (headlight/dashlight variances AND voltage dips) could be attributed to that connection versus the alternator?
Any other thoughts?
Seeing voltage spikes to 17 volts is what finally prompted my decision that it HAD to be the alternator causing the readings ESPECIALLY when I also saw dash/headlights vary in brightness. Prior to the rebuild, it almost always slowly dropped from mid/upper 13 volts into the 12's...and even 11's. Only two times had I seen voltage variances translated into headlight variances. Otherwise, mostly the gauge readings were the issue. However, when voltages dropped into the mid/lower 11's it sometimes resulted in lacking of cranking to restart. Plus, it goes without saying, I had to put it on a charger a lot....when sitting for days....as it often did.
I've only driven it 5 or 6 times since the rebuild but anomalies persist. Since the rebuild, one thing SEEMS to indicate improved/stabilized performance. Voltage on the first two drives stayed stable around 13.8V. However, a few days later after a longer 1/2 hour drive), I saw the voltage (once again) drop to the mid/upper 11's. On the fourth/fifth drive, headlights dimmed/brightened during the first few seconds of start-up. Voltage rose from mid 11's back up the 13's after approx 10 mins. (I can't remember how many days it sat, but it wasn't more than a week and I'd charged the battery after re-installing the alternator.
If the battery HAD gotten that low (again), would it be possible to SEE voltage variations in the headlights IF THE ALTERNATOR WAS TRUELY REPAIRED?
FWIW, I replaced the battery within the last 2-3 years. Because the charging issues I've rarely driven it over 20 miles for fear of being stranded. That's why I finally decided to rebuild it again. Because of the two incidents (one where headlights fluctuated...and the other where voltage dropped after a longer drive), my worries of being stranded are back. Should I call the armature shop and alert them I still have problems...and that the rebuild might be "problematic"? Is there any connection point in the wiring where both problems (headlight/dashlight variances AND voltage dips) could be attributed to that connection versus the alternator?
Any other thoughts?
Last edited by GREGGPENN; Oct 31, 2019 at 12:24 AM.
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Grounds. The big ones from frame to engine to battery. Also the power lead from battery to starter.
I added a 10 guage stranded ground wire between the alternator and frame to resolve voltage fluctuations.
Of course this was stop gap measures to help troubleshoot. Later I replaced both battery cables that were internally corroded.
I added a 10 guage stranded ground wire between the alternator and frame to resolve voltage fluctuations.
Of course this was stop gap measures to help troubleshoot. Later I replaced both battery cables that were internally corroded.
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Joined: May 2001
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From: Fairfax Virginia
If your battery is going bad it can make similar symptoms happen. If the battery is oxidized (inside) the battery voltage can go very high while trying to charge it. You are fighting the resistance of the oxidized plates in the battery and the "Surface Charge" can go up to your 17 Vdc range. The battery is supposed to help smooth out the highs and lows coming out of the alternator. Your battery connection might be corroded and cause issues like the ones you are experiencing. Like mentioned above the battery cables can corrode internally if the insulation was damaged. I have seen it happen several times over the years. It might help if you disconnected the battery and charge it up really well to ensure it is at full charge when you start testing the alternator
Where did you see the 17 volts? Have you measured it with a good multi-meter? Don't trust the gauges in the car, they are more for reference. The battery should not go below 10 volts if it is in "Okay" shape. Measure the voltage at the battery directly while the car is running to get an accurate reading. If your car is really getting 17 volts output then that is bad, why is the battery not pulling it down to 12 volts? The alternator has a good connection to the battery so I might suspect that the battery is part of the problem. Dead or dying batteries can display real high numbers but still not charge the battery. I have tested batteries for many years and have seen batteries do this a bunch of times in my life. If you really get 17 volts into the electrical system you might damage some of the electronics in the Corvette. That is way too high.
Make sure that your battery is in perfect shape and fully charged before testing the alternator. I use a Fluke Multi-meter with the Min-Max function. Using this meter I connect it to the battery and then start the engine with the Min-Max mode "on". This will show you how far down your battery voltage went while cranking the engine, if you let it site for a minute or two after starting the alternator should show it is working. The normal high should be in the upper 14 (~14.7) volt range for normal disconnect of the alternator. When colder it will go up a tiny bit to compensate for the ambient temperature. In hotter weather it charges using a lower cutoff like for example 14.3 Vdc
On my 1988 C4 I had a serious voltage drop between the Battery and the Fuse Box. It seems that the connection that fed the Fusible links was corroded and that caused an almost 2 volt drop inside the car and the engine compartment. After cleaning the post where they get their power and all the terminals the battery voltage appeared at the fuse block. The lower voltage made my stereo not work right and the lights were dim everywhere, several of the accessories would not run on close to 10 volts without issues. After the cleaning of the fusible link power connections the voltage drop disappeared.
Your car should be fine with the alternator you have. Installing a higher amperage alternator would require wire changes to handle the additional current to the battery from the alternator. On my C3 I ran the cable from the alternator to the Starter Motor where it met a large wire going to the battery behind the driver. If your engine is grounded then your alternator should be grounded.
The fact your lights are getting dim at idle is pointing to a bad battery to me at least. If the battery is not bad then the wiring for it is. Check your Fuse block and verify that it is showing the full battery voltage. If not find the source of power for your Fusible links and clean the connection to ensure they see full battery voltage. Have you checked to see that your engine is well grounded? I would do that before running new ground paths. The battery voltage should be the same when you measure it directly at the battery or when using the engine as the ground source.
Whatever you do please do not run the alternator without a battery connected, this can permanently damage the electrical system. We have seen it before here on the Corvette Forum... Parts are getting harder to find and more expensive than ever.
Keep us posted on what you find please, I am anxious to hear the cause of the issue.
Best regards,
Chris
Where did you see the 17 volts? Have you measured it with a good multi-meter? Don't trust the gauges in the car, they are more for reference. The battery should not go below 10 volts if it is in "Okay" shape. Measure the voltage at the battery directly while the car is running to get an accurate reading. If your car is really getting 17 volts output then that is bad, why is the battery not pulling it down to 12 volts? The alternator has a good connection to the battery so I might suspect that the battery is part of the problem. Dead or dying batteries can display real high numbers but still not charge the battery. I have tested batteries for many years and have seen batteries do this a bunch of times in my life. If you really get 17 volts into the electrical system you might damage some of the electronics in the Corvette. That is way too high.
Make sure that your battery is in perfect shape and fully charged before testing the alternator. I use a Fluke Multi-meter with the Min-Max function. Using this meter I connect it to the battery and then start the engine with the Min-Max mode "on". This will show you how far down your battery voltage went while cranking the engine, if you let it site for a minute or two after starting the alternator should show it is working. The normal high should be in the upper 14 (~14.7) volt range for normal disconnect of the alternator. When colder it will go up a tiny bit to compensate for the ambient temperature. In hotter weather it charges using a lower cutoff like for example 14.3 Vdc
On my 1988 C4 I had a serious voltage drop between the Battery and the Fuse Box. It seems that the connection that fed the Fusible links was corroded and that caused an almost 2 volt drop inside the car and the engine compartment. After cleaning the post where they get their power and all the terminals the battery voltage appeared at the fuse block. The lower voltage made my stereo not work right and the lights were dim everywhere, several of the accessories would not run on close to 10 volts without issues. After the cleaning of the fusible link power connections the voltage drop disappeared.
Your car should be fine with the alternator you have. Installing a higher amperage alternator would require wire changes to handle the additional current to the battery from the alternator. On my C3 I ran the cable from the alternator to the Starter Motor where it met a large wire going to the battery behind the driver. If your engine is grounded then your alternator should be grounded.
The fact your lights are getting dim at idle is pointing to a bad battery to me at least. If the battery is not bad then the wiring for it is. Check your Fuse block and verify that it is showing the full battery voltage. If not find the source of power for your Fusible links and clean the connection to ensure they see full battery voltage. Have you checked to see that your engine is well grounded? I would do that before running new ground paths. The battery voltage should be the same when you measure it directly at the battery or when using the engine as the ground source.
Whatever you do please do not run the alternator without a battery connected, this can permanently damage the electrical system. We have seen it before here on the Corvette Forum... Parts are getting harder to find and more expensive than ever.
Keep us posted on what you find please, I am anxious to hear the cause of the issue.
Best regards,
Chris
Le Mans Master
Joined: Oct 2002
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From: Las Vegas - Just stop perpetuating myths please.
Like Chris mentions you need to verify with another voltmeter/multimeter. You may need extension leads for this but they are fairly easy to make.
FWIW my '94 camaro voltmeter spends most of the ride at 18V but it does deflect when starting or using headlights.
FWIW my '94 camaro voltmeter spends most of the ride at 18V but it does deflect when starting or using headlights.
Safety Car
Joined: Aug 2013
Posts: 4,429
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From: Minneapolis Mn
Based on the description, have you checked the alternator charging wire? Run a jumper temporarily directly from the back of the alternator to the positive battery terminal and see if that makes a difference. Had my alternator rebuilt and still had issues, recrimped the ends and it worked for a year then acted up again. This time, I threw in the towel and got a new charging wire and it took care of my issues.
It was charging ok when start up, then voltage started dropping as I went maybe 5 miles or so with the original wire. If you want to do it, I got a 3' one from Summit Racing and it worked fine.
It was charging ok when start up, then voltage started dropping as I went maybe 5 miles or so with the original wire. If you want to do it, I got a 3' one from Summit Racing and it worked fine.
Last edited by hcbph; Nov 2, 2019 at 06:30 AM.
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Joined: May 2015
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THIS.
I replaced the alternator repeatedly - would get random low voltage readings, etc.
There is a fusible link underneath the battery that can corrode out. Also, corrosion can happen inside the crimp connections on the factory lead.
No problem since I ran a new wire directly from the alternator to the battery.
I replaced the alternator repeatedly - would get random low voltage readings, etc.
There is a fusible link underneath the battery that can corrode out. Also, corrosion can happen inside the crimp connections on the factory lead.
No problem since I ran a new wire directly from the alternator to the battery.
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Joined: May 2001
Posts: 4,757
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From: Fairfax Virginia
Hello there mt01,
Your point of the fusible links is what I am curious about. I have a 1988 C4 and the fusible links are located behind the battery a short distance. From what I have heard there is "supposed" to be a fusible link at the starter solenoid and when it blows it won't let the engine crank. I have looked on both of my Vettes and can't find that particular fusible link. I haven't seen it on the schematics either. I have never seen a Fusible link "corroded" through before. I have seen plenty that have burned thru when overloaded or shorted.
The fusible link is the last ditch effort to protect the electrical system. The fusible links on my car are all sealed in shrink wrap and appear fine on the outside. To be sure it is easy to use safety pins and test the fusible link for continuity. Just be sure to cover the holes in the insulation so water doesn't get in and corrode the copper wires. On my car when there was 10 volts at the fuse box so I had to remove and clean the terminals on the post mounted on the frame had the red wire directly from the battery. This post had seven fusible links getting their power from this point. The terminals were badly corroded where they attached to the post. A little wire brushing and they looked like new, after re-installing them I greased them and put a vacuum cap over the top of the post to prevent shorting. On my C4 the voltage immediately jumped up close to normal, after cleaning a few dozen connections the problem was eliminated, for now... It is now on my regular maintenance schedule so I don't forget to check the connections.
Having a clear path to the battery from the alternator is critical. I put a large wire on the alternator output and sent it to the starter where it connected to the wire feeding the starter from the battery. My C3 did not have the capability of handling 120 amps when the original alternator was a 40 amp unit. The wiring could not handle the extra current so I went around the Ammeter in the dash. This will keep the Corvette from catching on fire from overloading the original circuit.
That little post wherever it is on your Corvette is very important to the Corvette. With mine corroded the resistance increased dramatically. After cleaning the parts be sure to use a good battery grease to keep air from oxidizing the connectors again. Battery grease is great to keep the main connections from getting oxidized. Good clean connections at the battery are very important. Keeping it clean long term requires a bit more and that is where the battery grease comes in handy.
Best regards,
Chris
Your point of the fusible links is what I am curious about. I have a 1988 C4 and the fusible links are located behind the battery a short distance. From what I have heard there is "supposed" to be a fusible link at the starter solenoid and when it blows it won't let the engine crank. I have looked on both of my Vettes and can't find that particular fusible link. I haven't seen it on the schematics either. I have never seen a Fusible link "corroded" through before. I have seen plenty that have burned thru when overloaded or shorted.
The fusible link is the last ditch effort to protect the electrical system. The fusible links on my car are all sealed in shrink wrap and appear fine on the outside. To be sure it is easy to use safety pins and test the fusible link for continuity. Just be sure to cover the holes in the insulation so water doesn't get in and corrode the copper wires. On my car when there was 10 volts at the fuse box so I had to remove and clean the terminals on the post mounted on the frame had the red wire directly from the battery. This post had seven fusible links getting their power from this point. The terminals were badly corroded where they attached to the post. A little wire brushing and they looked like new, after re-installing them I greased them and put a vacuum cap over the top of the post to prevent shorting. On my C4 the voltage immediately jumped up close to normal, after cleaning a few dozen connections the problem was eliminated, for now... It is now on my regular maintenance schedule so I don't forget to check the connections.
Having a clear path to the battery from the alternator is critical. I put a large wire on the alternator output and sent it to the starter where it connected to the wire feeding the starter from the battery. My C3 did not have the capability of handling 120 amps when the original alternator was a 40 amp unit. The wiring could not handle the extra current so I went around the Ammeter in the dash. This will keep the Corvette from catching on fire from overloading the original circuit.
That little post wherever it is on your Corvette is very important to the Corvette. With mine corroded the resistance increased dramatically. After cleaning the parts be sure to use a good battery grease to keep air from oxidizing the connectors again. Battery grease is great to keep the main connections from getting oxidized. Good clean connections at the battery are very important. Keeping it clean long term requires a bit more and that is where the battery grease comes in handy.
Best regards,
Chris
