Service charging system light
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Intermediate
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Service charging system light
I just got my car back from getting a clutch put in and now when I'm coming to a stop with the a/c on sometimes the service charging system light comes on and goes off. with the a/c off the volts stays at 14.0 with the a/c on the volts bounce around from 13.0 to 13.8 sometimes drop as low as 12.3. I do have a pretty big cam and an under drive pulley that have been on for about a year and a half with no prior problems that I can remember with this issue. I did just replace the battery and did not change anything. Also cleaned the throttle body and didn't change anything. Also while driving with a/c on or off the volts stay at 13.9 to 14.1. I'm wounding if I should have my tuner bump the Rpms up a little or if I could be starting to have alternator or starter issues any ideas on where I should start or check out
Retired & lovin' it!
Joined: Mar 2005
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From: Jackson NJ
My suspicion is that your battery may be on the way out. The under drive pulley will also under drive the alternator & the condition will worsen at idle or low engine speeds plus made worse when there's more load on the system; i.e. when A/C is on. As the condition of the battery deteriorates over time, it is less able to take up a full charge. The alternator itself may also not be operating at 100%.
Thread Starter
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My suspicion is that your battery may be on the way out. The under drive pulley will also under drive the alternator & the condition will worsen at idle or low engine speeds plus made worse when there's more load on the system; i.e. when A/C is on. As the condition of the battery deteriorates over time, it is less able to take up a full charge. The alternator itself may also not be operating at 100%.
Melting Slicks
Joined: Aug 2014
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It's usually a sign one of the rectifiers has fried and is "semi" operational. The other 2 takes up the slack with enough rpm to keep output enough to operate, but at low rpm it will not be enough to maintain output.
Eventually that low voltage at low rpm will start dipping into 11 V.
I ended up getting a billet tech alternator. After taking apart the old one, you can see how it lacks the cooling design necessary to keep them from melting and shorting themselves.
Eventually that low voltage at low rpm will start dipping into 11 V.
I ended up getting a billet tech alternator. After taking apart the old one, you can see how it lacks the cooling design necessary to keep them from melting and shorting themselves.
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Voltage is too high for a bad diode.
Granted that the alternator being under driven is not helping out the problem, but if the the charging system/alternator ran for a year fine under driven, then time to just pull the alternator out of the car to clean and service it as a starting point.
The brushes may be fine (or need to be replaced), but just packed with so much dust in their housing channels that is creating a problem with then tracking the slip rings cleanly instead. As for the voltage regulator itself, it's so over designed and rated, that very, very seldom do they burn out.
So on that note, start here to pull the alternator to clean and check it out, and don't forget to dielectric grease not only the voltage regulator to the alternator body as you are bolting it back in, but the housing ears to the mounting bracket so you get a good ground back to the motor. Also, make sure to go through all the battery/ charging system wire connection points to clean and dielectric grease them as well.
https://www.corvetteforum.com/forums...y-voltage.html
Melting Slicks
Joined: Nov 2013
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From: Memphis Tn
use a volt meter to check the output of the alternator while the engine is running. it should be ~14.6 volts. if it is go to the battery and check and it should be ~13.8 or so. if not, check the ground wire above the starter.
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Negative probe on the multimeter on the alternator body itself, and positive probe on the actual threaded post of the alternator post under the back rubber boot (hold to the threaded post, and not just to the cable wire connector bolted to the post instead).
What is the output voltage of the alternator with your car idling, hence the alternator being under driven in speed?
What is the output voltage of the alternator with your car idling, hence the alternator being under driven in speed?
Thread Starter
Intermediate
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Well I replaced the alternator and the same thing is still happening. I'm wondering if my cooling fans are coming on I can hear the fan when I shut the car off but the under hood temps seem very high to me. I took the car for about a 2 mile drive after putting the alt on and everything under was untouchables when I got back. Also if the fans are not working properly that would put excess draw on the system when the a/c is on. Any other ideas
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From: Raleigh, NC
St. Jude Donor '15
Is it happening at low RPM's only or all over? The voltage on mine gets a bit low at idle too when all the fans are running hard (radiator and HVAC).
I used to get the charging message prior to bumping the idle up a little bit. I'd give that a shot.
I used to get the charging message prior to bumping the idle up a little bit. I'd give that a shot.
Thread Starter
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It's only at low Rpms I'm gonna try a new starter tomorrow and see if that does anything if not gonna take it to the tuner to have him raise the idle a little
Last edited by Brandon13; May 30, 2015 at 08:46 PM. Reason: Error
Race Director
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From: Raleigh, NC
St. Jude Donor '15
Melting Slicks
Joined: Nov 2013
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From: Memphis Tn
Safety Car
Joined: Feb 2007
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From: Opelika Alabama
MY 06 has done this forever. nothings wrong. just have your tuner move the threshold that the warning goes off at, in PLC terms it would be a "watchdog timer" my tuner saw all the stored warnings and "fixed" it for me without asking.
Thread Starter
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So an update on the situation im still getting the charging light I took it to my tuner and had him adjust the idle and no change. I checked voltage at the alternator and its charging at 14.8 at the back post. And at the battery is the same I think the issue is in the reference wire when I checked the voltage at that wire it is at 13.8 to 14.2 and the same at the fuse changed the fuse and no change. I also replace plugs and still no change. The wired thing is that the voltage only starts dropping after the car gets hot and the a/c on. While driving even with the a/c on voltage is at 14.1 and steady any other ideas.
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From: Raleigh, NC
St. Jude Donor '15
Mine dips down too sometimes, just no error message at the moment. I don't think the alternator puts out enough juice at low RPM's to cover the cooling fans + HVAC fans but that's just my opinion
I saw an old thread where someone installed some heavy gauge (I believe 0 gauge) wire from the alternator to the battery and to the starter and they had good results doing that
I saw an old thread where someone installed some heavy gauge (I believe 0 gauge) wire from the alternator to the battery and to the starter and they had good results doing that
Melting Slicks
Joined: Mar 2009
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Mine dips down too sometimes, just no error message at the moment. I don't think the alternator puts out enough juice at low RPM's to cover the cooling fans + HVAC fans but that's just my opinion
I saw an old thread where someone installed some heavy gauge (I believe 0 gauge) wire from the alternator to the battery and to the starter and they had good results doing that
I saw an old thread where someone installed some heavy gauge (I believe 0 gauge) wire from the alternator to the battery and to the starter and they had good results doing that
Try this....