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battery not charging, battery and alternator test good...long read

 
Old 09-12-2015, 11:29 PM
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Chicago1
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Default battery not charging, battery and alternator test good...long read

Well I'm stumped here I noticed the other day my battery was around 10.9 to 11.2 volts and the car was hard to start but it started..Went a few blocks and it never raised to the 13.8-14.1volt norm that I am use to. The car has 101k on it and the battery was bought new in 3/15 so only 6 months old. So I stopped at the store came out and tried to crank it over and no go, battery was dead. lucky I carry a portable jumper so I jumped it and went home. Charged the battery overnight and went for a cruise seen same thing with the voltage that it was never going up. I went to Oreilys and they did a test for me and they said it's your alternator. I though hmmm odd but ok and I head home


So I take the 2 mins it takes to get the alternator off and go have it rebuilt at a reputable alternator shop I used before.( I didn't check voltage out at the alternator) They assure me the have the correct parts for it since are alternators are a little more finicky because the pcm interface or whatever and the owner has a c5 .. He says no problem 4 hours later they are done said the coils were barely making contact and the put a new regulator in it. They do there checks and it passes their bench test. I take it home and guess what same thing battery isn't charging same low voltage I mean nothing changed whatsoever not better or worse exactly the same.. I called the shop and explained what I saw and they assured me it's working and pumping 14+ volts out on their test bench before they gave it to me.. So I take the battery and alternator out and take to autozone and they bench test it and they say both are good no issues. I asked if they put a load on it and they said yes its passing they tested each 3x.. Ok I scratch my head and I'm confused and decide to get a new battery or trade for a new one I should say. I go home install the new battery and alternator and no change...I read the voltage coming out of the alternator and it's 13.6 to 13.8 ..I just used a multimeter to the positive read lead/nut on the back of the alternator and the black lead to ground and seems to be reading correctly..So I limp the car it to autozone and they do a check on the car and sure enough he says your alternator is bad it's only putting out 11.5 volts...We both go wtf because I was just in there 15 minutes ago and it passed the bench test! I said it's brand new I asked for another new battery just because I'm fixated on the battery he was cool and I got my 2 new battery of the day and there was no change...So I am lost now


I don't think it's the alternator IMO and I have had 3 batteries tried out on it. 2 being new in less then 1 hour...What am I missing here? the only codes I have is RTD C0620H which seemed to happen right around the same time this issue happened. Also I took the plug out of the alternator just to check the output of those 3 pins and it reads what the battery is putting out on one of them I forgot what the other read..and of course once you pull that plug you get charge system fault which you will get that because it's unplugged duhh of course I plugged it back in and the charging system fault goes away...so that seems to be working correct? I haven't messed with anything lately this just started to happen all of a sudden.
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Old 09-13-2015, 12:51 AM
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Hmmmm!!
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Old 09-13-2015, 05:35 AM
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Fire it up and take your voltmeter and put one lead on the main stud on the back of the alternator and the other lead on the battery positive post. If you read any significant voltage then you have a problem between the alternator and the battery. The most likely area for the failure is at the starter. The charging wire from the alternator goes to the starter with a fusible link at the starter end. The starter terminal itself is also known to corrode and make a poor connection.
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Old 09-13-2015, 08:45 AM
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Do what Lionelhutz says and tell us what you get. We can start from there.

Here is the schematic. Note the battery is charged via the starter.





Charging System
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Old 09-13-2015, 01:47 PM
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Originally Posted by 8VETTE7 View Post
Got headers?? Likely fried wires near starter or loose/corroded connection at the starter as suggested above.
According to some of his posts, hes making over 600rw so I can imagine thinks have gotten really hot around the starter.
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Old 09-13-2015, 04:54 PM
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Examine the starter solenoid wires first, The connection between the alternator and batt live there!!!

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Old 09-14-2015, 10:29 PM
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Originally Posted by lionelhutz View Post
Fire it up and take your voltmeter and put one lead on the main stud on the back of the alternator and the other lead on the battery positive post. If you read any significant voltage then you have a problem between the alternator and the battery. The most likely area for the failure is at the starter. The charging wire from the alternator goes to the starter with a fusible link at the starter end. The starter terminal itself is also known to corrode and make a poor connection.
So I tried this and I got 9.6v..Is that significant? i have never heard of trying it this way. I assume i should be getting 0 volts? So I guess the issue is around the started area as you and others have mentioned?

Originally Posted by dadaroo View Post
Do what Lionelhutz says and tell us what you get. We can start from there.

Here is the schematic. Note the battery is charged via the starter.





Charging System
So I tried what Lionelhutz suggested and I got 9.6v..What exactly should I be looking for with this schematic if indeed I am not supposed to have 9+ volts.?

Originally Posted by 8VETTE7 View Post
Got headers?? Likely fried wires near starter or loose/corroded connection at the starter as suggested above.
Yup SW 1 7/8"

Originally Posted by ZZ06 View Post
According to some of his posts, hes making over 600rw so I can imagine thinks have gotten really hot around the starter.
I think over 700 now..I added more..

Originally Posted by Bill Curlee View Post
Examine the starter solenoid wires first, The connection between the alternator and batt live there!!!

Ok time to start pulling things apart oh and today was the first time I got charging system messages/codes..

thanks gents
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Old 09-15-2015, 12:03 AM
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Ya, 9.6V is very bad. You should have maybe a few 10ths of a volt there.

So, check the starter terminal where the connections are made and also check the fusible link. If you don't know how to check a fusible link you see if it's flexible like a piece of stranded wire should feel with no really soft spots or hard spots which indicate it's burnt open or the strands inside are melted. Also pull on it and see if it stretches which is bad since copper wire shouldn't stretch but the insulation is rubber so it gives easily.

If you look at that picture, the charging wire is the red one with the orange fusible link. It's kind if behind the other 2 wires.

The smaller red wire with the grey fusible link is the voltage sensing wire for the alternator. The big red one is the battery cable.
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Old 09-15-2015, 04:04 AM
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Ok gents thanks. ill have it apart this week on my next day off and update what I find.
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Old 09-20-2015, 09:55 PM
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Update:.Looks like my wiring to post on the starter was really loose.. I was able to loosen the nut all the way by hand that's how loose it was.I assume it being that loose that was the issue..gotta put it back together this week but I'm sure that wais it. At first I didn't see anything but once I jiggled the wire the wires just twisted on the post... All that wasted money for nothing I knew I should of posted first..I will update with the final outcome I'm working nights for a bit so put everything back together on my day off..thanks guys
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Old 09-20-2015, 10:12 PM
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Bet you found the problem. Loose connections are a nightmare sometimes. Not very obvious especially when tucked away like that.
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Old 09-20-2015, 10:46 PM
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Originally Posted by Chicago1 View Post
Update:.Looks like my wiring to post on the starter was really loose.. I was able to loosen the nut all the way by hand that's how loose it was.I assume it being that loose that was the issue..gotta put it back together this week but I'm sure that wais it. At first I didn't see anything but once I jiggled the wire the wires just twisted on the post... All that wasted money for nothing I knew I should of posted first..I will update with the final outcome I'm working nights for a bit so put everything back together on my day off..thanks guys
The thing I am wondering is where did you test and find the 9 VDC? Was that at the battery terminal? If so the connection on the starter is not the cause of the low voltage.

With the engine stopped you should have around 12.6 VDC at the battery post with a good VOM meter. If not you have a dead cell in the battery. If you have a standard battery you can purchase $2 hydrometer to test the individual cells Regardless if you have less than 12.6 on a fully charged battery this is the problem. The voltage should go to a little over 14 with the engine running.

I had a similar issue on my C6, very undependable and after a trip to the dealer, Autozone x2, and AAA and all reporting no issues with the battery or charging system I started checking it myself and discovered 2 cells were much lower than the other 4. The hydrometer works similar to a antifreeze tester and every cell should be very close with the same amount of ***** floating. If there are only 3 or 4 ***** floating in all cells the batter is discharged. If one or more cells have significantly less floaters those cells are dead and will not maintain charge. Not uncommon to have a bad battery especially if it has been significantly discharged once of more. Yours may be different but sounds highly suspect to me.
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Old 09-20-2015, 10:52 PM
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Originally Posted by lionelhutz View Post
Fire it up and take your voltmeter and put one lead on the main stud on the back of the alternator and the other lead on the battery positive post. If you read any significant voltage then you have a problem between the alternator and the battery. The most likely area for the failure is at the starter. The charging wire from the alternator goes to the starter with a fusible link at the starter end. The starter terminal itself is also known to corrode and make a poor connection.
Originally Posted by TX-Techman View Post
The thing I am wondering is where did you test and find the 9 VDC? Was that at the battery terminal? If so the connection on the starter is not the cause of the low voltage.

With the engine stopped you should have around 12.6 VDC at the battery post with a good VOM meter. If not you have a dead cell in the battery. If you have a standard battery you can purchase $2 hydrometer to test the individual cells Regardless if you have less than 12.6 on a fully charged battery this is the problem. The voltage should go to a little over 14 with the engine running.

I had a similar issue on my C6, very undependable and after a trip to the dealer, Autozone x2, and AAA and all reporting no issues with the battery or charging system I started checking it myself and discovered 2 cells were much lower than the other 4. The hydrometer works similar to a antifreeze tester and every cell should be very close with the same amount of ***** floating. If there are only 3 or 4 ***** floating in all cells the batter is discharged. If one or more cells have significantly less floaters those cells are dead and will not maintain charge. Not uncommon to have a bad battery especially if it has been significantly discharged once of more. Yours may be different but sounds highly suspect to me.
see above post from lionelhutz and not sure if you read but I went through 3 new batteries and 2 alternators. It's safe to say that loose connection is the issue..not the 3 new batteries and 2 alternators..
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Old 09-20-2015, 11:56 PM
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Yes, you do that test specifically to test the integrity of the wiring and in this case it was bad. Basically, you have the equivalent of a piece of wire between the alternator and battery. So, measure the voltage across the wire. If the wire is good the voltage should be very low. For certain issues I really like this method because it directly shows the health of the circuit.

Taking 2 different measurements at two different times is error prone due to the system changing between the measurements. This is one measurement that directly measures the integrity of the wire and starter connection.

Last edited by lionelhutz; 09-20-2015 at 11:58 PM.
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Old 09-21-2015, 09:28 PM
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Originally Posted by SuperVetteC5 View Post
Bet you found the problem. Loose connections are a nightmare sometimes. Not very obvious especially when tucked away like that.
You just said a MOUTHFUL and don't even know it!. To the OP Chicago, I bet you did find it. I just came through my own nightmare of electrical issues.. Will listen in to see when you start her up to see if that was it
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Old 09-22-2015, 04:08 AM
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Should have it going by Wed after I get up in the afternoon. These 12hr night shifts are kicking my butt!! I really hope that was it..Wonder why it came loose?
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Old 09-22-2015, 07:58 PM
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Originally Posted by Chicago1 View Post
Should have it going by Wed after I get up in the afternoon. These 12hr night shifts are kicking my butt!! I really hope that was it..Wonder why it came loose?
The kind of power your making id like to believe your cammed(among other mods obviously). Even if you don't have a lot of overlap, the motor will still shake n rock. Excuse my language fellas but as 8Vette7 and a few others know, this little bastard had me thinking I had a PCM or BCM gone bad. The car drove fine for a couple months after being built and it found its way loose. So its possible.


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Last edited by ZZ06; 09-22-2015 at 08:02 PM.
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Old 09-24-2015, 01:53 AM
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Good news and bad news..ao yeah looks like just the vibration of the cam and heat just made it came loose...good news is once I tightened everything up I put the alternator back on and volts went from 10 to mid 12s..definitely better but not the 13.9 to 14.2 I am used to..I went to Erics house and swapped alternators. I used mine on his and vice versa..when I used his I had 14.0v...when he used mine mid 12s...looks like they didn't rebuild it correctly or I would be finished...but the cause was that loose nut on the starter. Thanks for all your help gentleman.case closed now to deal with the alternator people again..
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Old 09-24-2015, 02:32 AM
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it really is one thing after another with these cars... glad you at least figured out what was going on, now hopefully you can get the right part to solve the issue... on a side note did you ever get the fuel pressure issue figured out??... I'm ready for you to get the car wrapped up so you can just get out and have fun with it
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Old 09-24-2015, 09:53 AM
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Having the alternator output basically operating with an open circuit on the output could have caused a rectifier diode to fail.
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