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'Check Charging System' message...

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I scanned and followed the shop manual for the repair.A new alternator worked for nearly a year with no Check Charging Message.
Run OT and come off and get the message again.Change the battery harness, same alternator, good for the last 4 years.
I do keep a spare alternator just in case.The car was charging the whole time all this was happening.
 
10
13
Exp. Type
HPDE
Exp. Level
5-10 Years
Denver
I too am getting a service charging system soon message popping up. It does not set any codes. This started for me on the last track session of the day on the cool down lap. It now pops up the message occasionally if I just go out for a drive. I will see voltage at 14.3-14.5 normal driving then the message pops and the voltages bounce around all over the place but mostly low, like in the 11s to 14 volts.

The alternators must not like the RPMs from the track, or the heat. Stock 2019 gt350. Original battery, so maybe that is getting old but seems more like alternator?
 
I too am getting a service charging system soon message popping up. It does not set any codes. This started for me on the last track session of the day on the cool down lap. It now pops up the message occasionally if I just go out for a drive. I will see voltage at 14.3-14.5 normal driving then the message pops and the voltages bounce around all over the place but mostly low, like in the 11s to 14 volts.

The alternators must not like the RPMs from the track, or the heat. Stock 2019 gt350. Original battery, so maybe that is getting old but seems more like alternator?

same for me. I did a battery monitor reset in Forscan and the error message isn’t popping up any longer but still large voltage fluctuations up to high 14’s.
 
8
13
Exp. Type
Autocross
Exp. Level
Under 3 Years
Post Falls, ID
So I swapped out the alternator and all seems well. 14.3 to 14.6 volts. I checked for loose or visibly damaged wires and couldn’t find anything. The plug on the back was stuck and took a while and some cussing and chucked tools to get off. I never threw any engine codes but I don’t think I have the right scanner. That was pretty frustrating I suppose I’ll carry around a spare. In any event thanks for the ideas and advice. One more thing learned about the car.
 
I had the same same check charging system light on my 12 Boss 302.
First time was coming off the track at Watkins Glen.
Scanned it and alternator showed bad.Replaced it and good for awhile and charging system light came back on and off.
Ended up changing the battery harness.That ended the problem.
FYI the trans has to be removed to R&R the battery harness.
I believe the one of the three tiny wires to the alternator plug gave up.
Gentlemen, Mostly a lurker here, 2012 boss 302, 46k miles. Check charging system message came on and off 3 or 4 times and then stayed off. Battery is 3 years old. My trickle charger showed and alternator voltage regulator fault. Went to 2 other parts stores, both confirmed voltage regulator fault. At high rpms/load the radio would cut off, or my phone or gopro would quit charging for a split second. During the alternator check i noticed one of the wires running to the positive terminal is crispy. Got hot enough to melt the terminal cover. I added a couple photos.

I replaced the alternator with an oem kit today. No more high rpm issues or accessories cutting off. Ive got a bluetooth obd2 adapter and it shows 14.4V. But putting a voltmeter on the battery shows 15.8-16.1 depending on if the fan is on or not. Needed an air filter and had the parts store check the new alternator and the voltage regulator failed the test again.

@gww52 who diagnosed your issue? And what was required to replace the harness? Thanks!

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I would start with changing that cable end. It looks like it was loose or the end came loose from the wire and got hot. This could be frying your regulators.
Easy enough. Ill give that a shot. What about battery type? The car died on me while running errands around town 3 years ago, oem battery made it a long time. I walked to advance and got the only battery they had on hand that would fit, duralast silver.
 
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38
I diagnosed it with my snap on scanner. There was no way to fix it without changing the harness.
You have to pull the transmission to make the change. Be very careful with the alternator connections.
 
The wire that looks crispy off the battery is hot to the touch key on. For the hell of it, i turned the key to on, didnt crank and every single light appeared on the cluster and all the warning messages came up. Check the battery, 12.2V. Maybe i get lucky and have a crappy battery.
 
After taking a break on the car sunday and monday I continued researching, found the link to wiring diagrams on this forum and determined the blackened wire in my earlier picture is the starter wire. That should be case grounded, so I'm not quite sure why that wire would be hot enough to blacken the bolt with key on, unless one of the grounds to the chassis is damaged. I'm not an electrical expert and appreciate continued input. I'm simply trying to run down all possible options before figuring out how to swap the positive cable harness. Thanks everyone.
 
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Never went to get a battery. Pulled the current one out of the car and it showed 12.56V. Started digging around on the car and found the electrical tape holding the harness to the passenger side shock tower failed, allowing the harness to swing over close enough to the exhaust manifold to melt the tape and plastic sheathing, exposing the insulated wire attached to the circuit breaker on the positive battery terminal.

The stud for the wire to the underhood fusebox got hot enough to fuse itself to the bolt so resigned to cutting that off. I checked as many grounds as I could get to and they all looked good. Cleaned up the connections to the positive battery terminal connector, little bit of dielectric grease everywhere, new wire loom plus heat tape on the bit of harness that melted and a metal zip tie thru the holes on the shock tower.

Drop the battery back in the car and turn the key, only normal lights appear on the dashboard. Fire it up, hop out and put the multimeter on the battery, 14.6 volts! Too late to drive it without waking the entire neighborhood.

Got very lucky the wires were not melted. My guess is the combination of heat in the wires and 12 years of crud on the connections was causing extra resistance and the ecu was asking for more voltage from the alternator at all times, just a guess though. It may not have needed a new alternator, test drive tomorrow.

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Test drive between rain storm last friday went well. The car has a tiger racing hood on it and has seen some rain during trips. The cycles of moisture and heat probably contributed to the electrical tape failure, allowing that part of the harness to get too close to the passenger side exhaust manifold. I can now grab and hold the post on the battery while its running without immediately burning my fingers. More importantly, voltage at the battery is back to normal, showing between 14.1 and 14.4 instead of 15.8 to 16.1 in the multimeter.

Keep an eye on that harness on the passenger shock tower folks!

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