So my car kept dying, even after a new battery. I recently took it to the shop where they changed the alternator to a new one, and also the timing belt. When I get it back (I also got a new battery under warranty) the ******* car starts and it charges at 14 volts, and then it drops down to 12.4 or so. My mechanic is clueless and so am I. What could be wrong with this POS?

 

Some background information. One day after I woke up I go to use my car and it doesnt start, nothing happens. I figured something happened and I left something on and the car died. Went to get a new battery. After I did the car ran fine for a week and then died again one morning. So I figured it was the alternator. So I changed it.

 

Maybe a loose belt ?

 

I felt it, didnt feel loose

 

do this,push down your rear seats,close and lock the doors and look inside the car to see if your trunk light comes on. Happened to me with my 1997 vw jetta

 

Well my main concern is that the car starts and is running at 14 volts for a minute, and then it dips to 12.4. Thats not good, that means the battery is powering the car not the alternator..

 

should I change my grounds?

 

Yeah, you have to make at least 13.5 iirc to charge a 12v battery. Are you sure the new alt is good? Auto parts stores can check them for free or small charge, I would start there. Check, clean all your connections, not just at the battery.

If not that, are you sure everything is off when this happens? Any crazy aftermarket stereo or other equipment that draws power? The other possibility is a short somewhere, but that's usually something small that drains your batter over time. There is a way to check for current draw with the car off using a multi-meter, but to me it sounds like a bad alt.

I should also ask, is it 12.4 v charge at idle only? What about different RPM? It should be at 13.5 and over even at idle, but even at 12.5 should increase with higher rpm.

 

Well I changed the alternator, I doubt a brand new one would be bad.. No RPMs do not influence the volts at all, if anything they make it lower...

 

Okay, so we can say with fair certainty that even if your alternator is good, the charge is not getting to the battery. Check the connections at the alternator, clean them etc. Considering that's all you've touched, that's likely the problem.

Also, I you may want to verify the voltage with a multi-meter or other gauge at the battery and alternator. I trust Audi gauges like I trust a fat-kid with a smartie.