Low battery warning - only at start
I've got an issue with my GT V6 that occurs infrequently. I get the low battery warning message and picture when I start the car. It seems to happen if I have either a) not driven the car for a while or b) driven v v v short distance (ie moved it around on drive)
Some history and what I've done so far...
3 or 4 months ago I was getting the same and the car was getting v sluggish to start, including needed to be jump started a few times. I ordered a battery, turned out to be the wrong size, but we have another Alfa in the Boysie stable, a 156 s/w. I had replaced a battery on this a while ago (with a cheapy - due to impending sale of car), and that was actually a smidge too small, so... instead of sending back new battery I swapped them over, and hey, they both fit correctly (I needed the car next day, did not want the hassle of returning a battery)
So, my GT has a 6month old batt on it - but it still occasionally reports the low battery error at start. It's not got so bad I've needed a jump yet.
I invested in a multimeter to try some home diagnosis, and discovered that the voltage when the car is idling is at approx 14v, I have assumed this means the alternator is working OK. When the car reports low battery the voltage is at approx 11.5v. After a run it's back up to 12.6v, so hopefully ruling out the alternator.
I have checked for all interior lights going off (boot/glovebox/interior)
So, could it be that the donor battery from the 156 is just not up the job at startup from cold - resulting in the error shown, and I need to fork out for a more expensive battery. I assume a v6 takes a bit to turn over comapred with the 1.8 ts, or do I need to look out for a battery drain ...
All and any ideas welcome. Thanks
PS - Meant to say I replcaed blown sidelight bulb last week, thinking this may be causing some sort of short. Unfortunately it has reported the error since.