I have a 2002 X-Type. The car needed to be jump started the other day so I went and had it checked out. The Battery tested as good and the Alternator tested as good as well, however the alternator was only putting out 11.9 volts with no load and 12.9 volts under load. While the alternator output seemed low, it seems like it should still supply some volts to charging the battery therefore I presumed that if I just make sure that I keep the battery charged, all would be well.

I bought a new handy dandy charger and made sure to top the battery off completely. I reinstalled the battery went to bed, got up the next day, drove 29 miles before the low battery light came on and then the car shut down shortly thereafter.

Even with no alternator assistance I would think that the battery would have made it farther then 29 miles. It is seeming to me that I might have a power drain somewhere and maybe that is causing my alternator to go bad.

How to I begin to diagnose this? Has anyone had similar problems?

Thanks!

 

even though the battery reads ok after toping off, if it is losing power that quickly (assuming you DON'T have a power drain) it could still be a bad battery. i've had this problem with my past vehicle and after having the batter thoroughly tested it turned out one of the cells in my battery was the culprit. it could charge up fully but was not able to hold the charge. getting a new battery solved this. hope this is your problem and nothing more pricier.

 

Good morning, A good "shadetree" way to check for a battery drain is to disconnect the earth cable and then barely touch it back to the earth battery terminal. There will always be a small spark due to the car's power/memory requirements (unless the battery is 'stone' flat). However, if you observe a BIG spark, chances are that you have a power drain i.e. hard ground, closed switch, mismatched component,etc. Also, funkdoktor is 'spot on' about the possibility of a new battery being defective. Over the years I've had several bad ones. They even fail in NON British iron-HMM?!?! Good luck, Andy

 

Alternator issue possibly. I measured 11.1 volts from alternator wire at the alternator and 11.1 volts at the battery (both measurements taken while running at idle). One weird note was that it spiked once when revved to 13.1 volts however I wasn't able to repeat that spike).

Does this sound like a bad alternator? Hard as heck to get to! Thank you!