Aternator Overcharging
 

Hey all, so a couple days ago we discovered that my alternator was overcharging and melted the plastic cover that goes on top of the alternator. After removing all the melted plastic, I had to tighten the 12mm nut down. I ran the car with the AP plugged in and the voltage peaked at 15.1V during a 20 minute drive and stopped driving it immediately after before anymore potential damage can happen.

I currently have the alternator removed, also had to pull out the wire as well since it is cooked and will get it checked out. Since our voltage output are controlled by the PCM, I just wanted to get an idea on what ground locations I should inspect to ensure the PCM isn't trying to compensate for possible low voltage readings due to poor connection. Thanks!

The grounding locations are on the drivers side engine above the oil level sensor, passenger side frame to lower intake manifold, and there are a couple on the frame above the fans under the intake tray. There are also various small ones form the engine bay harness to the chassis. And really many all over the car.

The Accessport is showing the voltage that the ECU see's. Not what the Alternator is putting out. I don't know why it would be overcharging. I would start with a new alternator. Did it just spike up there after a Hard rev or did it sit at a steady voltage above 14?

My average reading was between 14.1 - 14.3 and sometimes goes up 14.8 - 15.1 intermittently. I did measure with a multimeter on the alternator itself while idling and was around the same steady 14s while the battery tested at 13.8 at the time. I still have no idea why it got hot, all I know is the bolt was loose and I tightened it down... But I dont know for sure if it loosened due to the plastic melting, or was already like that beforehand.

15.1 is way too high, max I've seen is 14.7, and that's a brand new alternator.

Yeah. We just had the alternator replaced with a reman unit. I also replaced the power wire since it is toasted with a new 8 gauge wire. Took it for a 25 minute test drive, and it averaged 14.1 and never went above 14.6 during normal driving. It's weird though, everytime I attempt to park up my driveway towards the garage, I ended up hitting 15.7 for a split second and it dropped right away to 14.1 again.

Before the reman, that 15.1v was also going up my driveway momentarily. Do you think the voltage peaking that high is based on the amount of load I'm putting going up on an incline? I'm worried that I may have a bad ground from this point somewhere, but I have no aftermarket electronics whatsoever and never touched any other electrical components.

if it's just a spit second I would say that's normal.

if it's consistence then u got a serious problem, undercharging is easy, u worst case u need a tow truck, new battery and alternator, overcharging is BAD, might cost u a tow truck, and every electronic on the car.

Hmm, I don't think mine ever goes above 14.5 at any load, even at full boost. I will keep and eye on it and see.

Yeah, it's definitely only for a very brief moment. I'm using my AP to see the peaks and lows after driving around for quite some time. I'll make sure to keep an eye on it.

Would really appreciate that, thanks a lot. I'm going to go over the car's grounds and see if there are any potential problems.