My 2001 C5 keeps throwing up the charging system fault every 2 minutes or so and there is nothing wrong with my charging system at all it is really perfect and no charging issue at all. I keep watching for new places to look and other owners fixes and the systems so forth. I just wish i could figure it out before i have to take it too a dealership. Could it be a simple ignition switch or is it a ground or plug just a little off ? no way what is it then ? how do i pinpoint it and make it stop throwing up the message ? please ideas ?

 

Does sound odd but you don't say what you have checked to be sure nothing is wrong. Have you checked out the heavy gauge grounds from the battery negative post, to the engine block (on passenger side of engine). and the engine's ground strap to frame maybe worth checking too (drivers side of engine seen better from below the car).

 

Did this begin happening all of a sudden and out of the blue? By any chance, has the alternator been replaced? If yes, that's most probably the reason why. Click here for more details.

 

yes i bought the car from a car lot and right before i purchased it the alternator and battery were replaced. so if it had the charging system fault before those two items were replaced i don't know..the car is charging exactly correct and it has no issues with the charging system at all...? but the fault comes right up when i start thecae maybe 30 seconds after i start it then it continues to ding and reappear on my info screen

 

as far as the ground straps I did look at those but i did not take them off and clean them as they looked fine i have not really looked under the car at the starter or ? i did look at the plugs and connections under the battery and did clean up the connection under there that connects to the frame and has two smaller wires at that location and same fault ... my mechanic did check the alternator as we would had right from the start but no luck it is perfect.. 14.3 volts 14.4 volts so we cant pinpoint where the fault is coming from but it is definitely consistent all the time so nothing funny happening like periodic or gauges fluctuating or any of that at all.. the car starts right up everyday runs fine no electrical issues or signs....?

 

i just don't know why it would be the alternator if it is charging perfectly and the regulator is working correctly .. could it be the ignition switch somehow ?
thats the only thing i could think of ..? or the computer but that has also been replaced a couple years back and nothing else is pointing to that so the situations i see on line tube are starter solenoid post loose or cable is loose or I've heard of ground cables not grounding all the way which is very hard to pinpoint or trouble shoot in fact this fault is very troubling that it cant be trouble shooter ? or if anyone knows how to pinpoint or troubleshoot ? my mechanic is baffled as well as everything is right on point as far as the alternator regulator and battery and ......

 

This is a known issue and has been extensively documented. C5s are extremely "picky" regarding alternators.


But it probably has the wrong voltage regulator. Even if the replacement alternator is listed as "correct", its voltage regulator is most probably not the right one. Check the link I gave you in Post 3 above. It explains why and provides links to the right voltage regulators.

Plenty of horror stories here in the forum if you search

Just to cover all bases, what's the voltage directly at the (+) battery post using a multimeter?

 

hmmm ok that could be the answer but i still wonder why everything is fine with the regulator as it is operating correctly but throwing a fault as well... I had a weird feeling about this regulator right from the start but let me talk to my mechanic about all this to see if he remembers the voltage read at the battery as you asked about i don't remember but as we surely checked and would have remembered if it was anything other then the respective gauges were reading (voltage reading inside the car on the screen) I would have remembered , but i really appreciate your help everyone !! I am going to ask my mechanic and see if we need to replace the internal regulator ...

 

The one thing i don't want to do and cant do is to start buying items and just replacing them until i find the right part replacement .. that is way to costly and not the correct way to solve this issue and as I knew when I posted this issue that this recommendation would be offered .. I just cant replace something that is not broken i would however like to troubleshoot the fault then track it down as by past experiences of others such as you all thank alot your awesome and by just thought process or tracking down the pin point area that is causing this problem .. Then i can share exactly what is is and how i tracked it down and then post it to help any others like me in the future but so far i am still in square 1 with only suggestions that are great and I will look to see what regulator i have but that involves taking the alternator out of the car ? I just cant ask my mechanic to check which regulator i have in my alternator can i without paying him for that ?? Or can i look and tell what regulator is in it without taking it out ? ?

 

I already gave you twice the link where everything is explained in details. It seems you haven't read it because you haven't returned with any questions regarding that and still wonder the same thing.

If the voltage taken directly at the battery with a multimeter matches the voltage at the alternator, and it is around 14V, then most probably the voltage regulator, even though is working, doesn't have a "soft start". That is reason enough to trigger the fault, as explained in details in the above mentioned link.

If the voltage taken at the battery is substantially lower than the 14V your mechanic found at the alternator, then everything changes, but then I hope your mechanic would have caught that... Nevertheless, I asked you about it to be on the safe side.


The voltage as reported by the gauges and DIC is usually lower than what is measured directly at the battery, that's why I asked you for the voltage at the battery. The reason for this is that both, gauges and DIC, take their reading downstream the ignition switch and usually there's a voltage drop at the switch.


Agreed, but then if your mechanic is not familiar with the C5 peculiarities, as it seems so far, you would have to be ready to do some troubleshooting yourself. This would require, at the very least, to get a multimeter. You​ would also need to do some research.


The idea was not blindly offered, as you imply. I suggested this after reading what you wrote. As I already mentioned, this is a known issue and has been extensively documented. Search is your friend... click here for a case similar to yours. If replacing the voltage regulator is not an option your mechanic is willing to take and you are not up to that, then I'm afraid that your only remaining solution is replacing the alternator with one that works in a C5. For some people, this has been a trial-and-error ordeal.

 

I do remember that the voltage was the same in all three places. as we did test that to try and run down the issue but there is no clear sign that we have found that would tend to point us in the correct or narrow down location. I do apologize if I sounded a bit pompous I can assure you it was not my intention. I just am frustrated that this alternator and battery were replaced right before I bought it so I don't know if the fault was the reason they were replaced ?? I am hearing you mention soft start which is sounding somewhat familiar. I also thought i heard something about that so many starts must happen before the code is cleared or anyway I just cant start replacing items in hopes that it is the problem and so on .. but I could just return the items as I test them on my car and whatever doesn't fix it ill just return it and keep going but what if it is a lose wire i cant see or not a part thats bad then i will be doing alot for nothing so I just want to figure out a way to isolate and troubleshoot ... I appreciate your help believe me thank you very much I will keep looking around and i guess ill purchase a multimeter as well.. and alot more research too..

 

What's happening to you is not uncommon, just that in your case things are are little muddied, since you were not the one who replaced the alternator.

This can be confusing for people not familiar with the peculiarities of the C5 because if you have the alternator tested, it will pass as "good".

The important thing to understand is that it's not that the alternator is bad, is that it has the wrong voltage regulator. Because of this, 2 things could happen: either the car's PCM won't be able to turn it on, or it can turn it on, but it doesn't have the required soft-start. Since yours is turning on, as per the 14.3V you mentioned were read, then most probably your problem is that it doesn't have a soft-start.

NOTE: you need to verify that voltage directly at the battery is no more than .2V or .3V less than directly at the alternator.

Your car is a 2001, therefore your voltage regulator should be an M530.


-More Details:
What makes this alternator so peculiar is that it is excited when its regulator receives a turn on signal of 10v at limited current provided by the PCM through the L wire. Not all regulators accept the turn on signal provided by the C5 PCM.

Another distinctive attribute described by Lionelhutz in this post:

 

I totally get it now ..wow this is a great forum I just am very thankful for all the education and the "real" repair method. I am saying that this must be something that is oblivious to the aftermarket alternator remanufactures.. As they could be or are rebuilding these alternators with the wrong regulators in them so in order to get the correct alternator with the M530 regulator I wouldn't be able to ask for an alternator with that regulator in it ??? So now I know how to repair this issue I have to ask if I can order this M530 regulator and I can install it external ? Is that correct ? And then after I install it will I need to do anything for the fault to clear or will it just not appear any longer ? I guess is it as simple as a install of this part and thats it ? Thanks for the clear experienced repair and info ..really awesome I am thankful !!

 

You're welcome!

The voltage regulator can be purchased here (click on the link):
97-01 Valeo Regulator 2542521B (M530) $32.99

I suggest you do some research on how to install a voltage regulator to decide if you're up to it.

Don't forget to read voltage directly at the battery and verify that it is no more than .2V or .3V less than directly at the alternator. For example, you mentioned that at the alternator you have 14.3V, then at the battery you should have no less than 14.1V, or 14V at the most.

 

Ok i have ordered the part and I looked at a video on how to replace a voltage regulator and it looks very simple. I will be keeping you posted after replacement ..Thank you very much for your help I wouldn't have been able to do this without your help so Awesome !! Thanks so much!!

 

Please, let us know how it goes

I keep insisting on verifying voltage directly at the battery. You need to compare it to the one that was taken directly at the alternator, as I have mentioned. If it is not within acceptable range, your problem might have a different origin. Again, this is just to be on the safe side, as I hope your mechanic would have caught that.

 

May I ask a dumb question - should the engine be running or not?

 

Engine running

 

My equipment is dated ‘90s - got a dial reading at 13.5 at the battery - 13.6 maybe at the alternator do I have a problem?

 

That means that your voltage drop in the "alternator-starter solenoid-battery" chain is just .1V

That's very good!