2015 Mirage intermittent battery light and intermittent not charging problem

[Fummins]

I've got a 2015 Mirage in the shop with 500xxxkms/310k miles. The complaint was battery light would come on, was hard to start once. Not a lot to go on....
I drove it in, battery light was not on and the alternator was putting out about 14.5volts. I couldn't find anything wrong but wanted to figure out why the battery light came on. Figured maybe a wire along the usual place was giving signs of failure. I did the wiggle test with the engine running and camera pointed at the cluster and could not get the light to come on. I even unplugged the connector at the alternator and the light still didn't turn on. The only thing that happened was it started charging higher, up around 15volts.

Eventually, I cut the wiring harness open and discovered one small wire leading to the alternator connector had a hole in the insulation and was corroding so I cut out the old crapy wire and spliced in and soldered a new piece. That wasn't the problem. One out of the dozens of times I started this car, the battery light did come on(with it running), and it was not charging. I can't remember if it was before or after I repaired that wire though...

I could not get it to act up anymore so I kicked it out the door and told the driver to bring it back if the light came back on. Car was used a few hours yesterday and came in this morning running good. Driver went to leave and the battery light was on so they came and told me right away. I pulled the car behind the shop and left it running so I could try and troubleshoot it a little bit. It sat there for maybe 5-10 mins before I went to drive it into the shop and it was already dead. Key on, engine off, battery drained enough that it wouldn't start or even release the shifter lockout solenoid. I pushed it inside, hooked the battery charger to get it running. Started it up and the battery light came on with the charger unhooked. I had to work on something else more pressing so I just shut it off and left the charger on it so it'd start later to move out of my way. An hour or so later I pulled it out of the shop then back inside and the battery light was off and it was charging properly....

I'm back at this thing trying to figure it out. A visual inspection of the wires under the hood looks like all the other cars. Nothing burnt or corroded badly.
I can't remember if any wires for the alternator circuit run through the infamous kick panel connector. I'll probably take a peak there first. Then test the battery. If all that checks out then I'll probably turn to the service manual and play along through the flow chart. If all that fails I'll probably throw an alternator at it. I haven't seen one fail one minute then not the next though. This seems like bad connection or???

[Fummins]

Well, time to fire up the parts cannon. I don't know if the alternator is hooped or not but I have a pile of them so I'm gonna give that a go. It's a good thing these things don't fail often, this thing was a sob to get out. The power wire and connector were fine, upper mount was easy. The lower mount bolt is a pita. I can't imagine having to do this job if I lived in rust belt Ontario or New York! The bolt was siezed, couldn't get a hammer in there. Ended up clocking the alternator all the way forward and hitting the head of the bolt back and forth with a chizel til it finally moved a little.

[CROSSBOLT]

Can't wait to read the final on this one! You the man, Fumm!

[mitsumi]

Mine is a 2015 MT, I just have an issue also with my voltage since Monday, my only concern is, the battery symbol doesn't appear even if my battery is way below 12v, when do the battery symbol should appear?

Also, my battery goes 12.9v after a few mins when I turned off the engine.

[Update]
i checked my alternator bolts right now, but it weird that its loose, its not that tight but im pretty sure I did tighten it when i changed the belts. But hopefully this fix it.

[Fummins]

Mine is a 2015 MT, I just have an issue also with my voltage since Monday, my only concern is, the battery symbol doesn't appear even if my battery is way below 12v, when do the battery symbol should appear?

Also, my battery goes 12.9v after a few mins when I turned off the engine.

Does your battery light turn on when you return the key to run and engine NOT running?
If your voltage is under 13volts when the engine IS running it then something is wrong.

[mitsumi]

Does your battery light turn on when you return the key to run and engine NOT running?

No the battery light didn't turned on.

If your voltage is under 13volts when the engine IS running it then something is wrong.

After i adjust the alternator and tighten the bots, the voltage prior starting at 14.1. Tomorrow morning Ill check again see if the voltage drops again.

[Update]
So this morning i did try to check and it seems the voltage didnt drop below 13 volts, at start theres like a hiccup then it starts.

[Fummins]

No the battery light didn't turned on.



After i adjust the alternator and tighten the bots, the voltage prior starting at 14.1. Tomorrow morning Ill check again see if the voltage drops again.

When you turn the key to the run position, the red battery light should turn on.

When you start the engine the light should go out.

There's a chance you don't have a battery light, but I doubt it....

Check voltage at the battery with the engine running. Normally I see around 14.0-14.6 volts.

If your battery isn't charging when the engine is running, it'll still run until voltage gets down to around 8-9 volts then it'll just die.

[mitsumi]

@Fummins
Oh sorry, I thought when you say run was the engine is already running.
Yes, the battery light turns off when I start the car, mine is push start btw.

[daleWV]

Intermittent like that sort of reminds me of worn-out brushes in the alternator.

[Fummins]

Intermittent like that sort of reminds me of worn-out brushes in the alternator.

Have you seen that before? I did end up replacing it and so far so good. But I said that once already. I checked on it throughout the day with the gps stalker and voltage seemed to be good. I’ll call it fixed if it doesn’t come back this week.