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-   -   Battery light and "check charging system" warning (https://www.allfordmustangs.com/forums/2005-2010-mustang-gt-tech/926842-battery-light-check-charging-system-warning.html)

LosAngelesGT 01-07-2016 09:01 PM

Battery light and "check charging system" warning
 
Hi guys,

The battery I have is less than a year old. The alternator is less than 4 months old (replaced it due to the misfire errors) and everything has been fine since getting the alternator changed out - until last weekend.
I made about 6 trips up into the mountains for snowboarding the last few weeks and subjected my car to sub freezing temperatures (Don't know if thats a factor?)
Last weekend on my latest trip I was hooning down a 2 lane desert road. Averaging about 120mph for 5-10 minutes, and flooring it whenever I pass someone.
All of a sudden the battery light and check charging system warning kicked in. I saw the battery charge gauge start dropping and quickly killed my heater, shaker1000, and headlights (just kept the fog-lights). After that it held steady and the warning went off until I turned the headlights on again and the warning came back. After about 5 minutes the warning went away all together, and the rest of the 2 hour drive was fine even with the shaker1000 and headlights.
I took it to the mechanic the next day and of course everything was fine - held charge at 13.6v despite blasting AC, Music, and lights on. Next they pulled and played with the wires to see if there was something loose. That wasn't it either.
This last week the car has been completely fine ( I daily drive her, at least 30 miles a day).
Was this a freak occurrence or is my alternator going out again? I want to go snowboarding again soon and the last thing I want is for my car to die on the side of a desolate desert road, with no cell reception.

94vert 01-07-2016 11:25 PM

11 Attachment(s)
I would say its the alt going. Have you checked the battery by itself? too me it sounds like the alt is not charging properly.

Bullitt95 01-08-2016 11:39 AM

It does sound like the alternator may be on the way out again but I'd check the power wire connection to the back of the alternator in case it's slightly loose and making poor contact.

MustangLife 01-08-2016 02:07 PM

Could this not have had anything to do with the cruising speed of 120+ for a long duration? I would think that could contribute to some warning lights. I wouldn't know for sure as where I live that would be impossible. haha I have driven between Vegas and LA once a couple years ago and can totally see how you did it where you live. I was in a rental car that would barely do the speed limit and my friend and I were just happy to make it there without breaking down as the rental car had issues in the middle of the dessert so I know your fear as well... haha

Yeah is your sound system stock? If you have altered it in anyway you may want to consider a capacitor for the amps/sub...

ski 01-08-2016 04:07 PM

The alternator brushes can bounce during long periods of high vehicle speed, which will interrupt the alternator field current and produce a large negative voltage spike on the alternator output that causes an error in the ECU.

LosAngelesGT 01-08-2016 07:55 PM

Quote:

Originally Posted by ski (Post 8113850)
The alternator brushes can bounce during long periods of high vehicle speed, which will interrupt the alternator field current and produce a large negative voltage spike on the alternator output that causes an error in the ECU.

Super interesting reply. What exactly is an alternator brush? How does one prevent it from bouncing (aside from slowing down:wink:)?

LosAngelesGT 01-08-2016 07:59 PM

Quote:

Originally Posted by MustangLife (Post 8113658)
Could this not have had anything to do with the cruising speed of 120+ for a long duration? I would think that could contribute to some warning lights. I wouldn't know for sure as where I live that would be impossible. haha I have driven between Vegas and LA once a couple years ago and can totally see how you did it where you live. I was in a rental car that would barely do the speed limit and my friend and I were just happy to make it there without breaking down as the rental car had issues in the middle of the dessert so I know your fear as well... haha

Yeah is your sound system stock? If you have altered it in anyway you may want to consider a capacitor for the amps/sub...

Yeah, at first I thought I had gotten the alternator too hot while cruising at that speed for a while.
Aren't those desert roads great? So much hooning potential. Although the novelty wears off when your car looks like its about to fail - and you know your 10 miles from the nearest gas station and with zero cell reception! :|
Car has a stock shaker 1000 system, so it shouldn't need a capacitor right?

LosAngelesGT 01-08-2016 08:02 PM

Quote:

Originally Posted by Bullitt95 (Post 8113378)
It does sound like the alternator may be on the way out again but I'd check the power wire connection to the back of the alternator in case it's slightly loose and making poor contact.

I didn't actually take off the intake + throttle body, but with the mechanic I did some pretty vigorous wiggling and tugging on the back wire of the alternator while he monitored the charge...We got nothing, charge level never missed a beat.

LosAngelesGT 01-08-2016 08:02 PM

Quote:

Originally Posted by 94vert (Post 8112626)
I would say its the alt going. Have you checked the battery by itself? too me it sounds like the alt is not charging properly.

Battery checked out fine

94vert 01-08-2016 09:39 PM

11 Attachment(s)
poor grounding somewhere? is the main ground in good shape? is the stereo grounding still making good contact? I don't think driving at high speeds are going too cause any issues. I've done many 70-90+ mph 1000 miles runs with no problems with many cars. Driving 17-21 hours with only short breaks for gas and food. I say check all your grounds, the alt harness, also did you hear any noise from the alt's pulley? or is the belt too loose/tight? check the idler pulley, I had one fail on my 4.6L explorer. it caused a similar issues like yours.

05capepony 01-09-2016 09:01 AM

Had the same issue. Turned out to be bad contacts on the alternator to regulator connections. This will cause the battery light as the computer senses a ground fault. You will need to remove the alternator and remove the regulator. Replace the regulator while you are at it. Clean the contacts on the alternator and add some di-electric grease install new regulator and you should be all set.

ski 01-09-2016 02:24 PM

Quote:

Originally Posted by 94vert (Post 8114378)
I don't think driving at high speeds are going too cause any issues. I've done many 70-90+ mph 1000 miles runs with no problems with many cars.

Big difference between 120 mph and 70-90 mph in relation to the rpm of components that increase with engine rpm.

ski 01-09-2016 04:37 PM

Quote:

Originally Posted by LosAngelesGT (Post 8114170)
Super interesting reply. What exactly is an alternator brush? How does one prevent it from bouncing (aside from slowing down:wink:)?

One of the components of an alternator is a rotating electromagnetic coil, or armature.
The armature receives power from the car's battery as follows:
(1) The battery is connected by wires to stationary, spring loaded carbon components (brushes) mounted inside the alternator.
(2) The brushes remain in constant contact with rotating metal slip rings mounted on the armature shaft.

If the problem doesn't happen at lower speeds, then you have the answer to your question.

LosAngelesGT 01-11-2016 02:44 PM

Thanks for the feedback gentlemen!
I did some more high speed runs and the problem didn't reoccur.
I took it to the mechanic again and he checked the grounding and connections and found nothing, so seeing as my alternator is under warranty, I just decided to get a new one. See if that solves it.


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