The battery on my Xzara went flat and " Battery Charging Fault" message came up and the battery charging light stayed on.. The garage checked the battery changed the alternator. 2 days later the battery was flat. They bench tested the alternator, they tried a new battery. They ran a jump cable from the battery terminal to the battery and registered a charging current but there was no voltage regulation goiong on.
They are currently stumped. They have phone several Citroen contacts with zero results.
Is there some sort of voltage regulation between the battery and the alternator that may be causing this problem.
If battery is fully charged up car runs perfectly with no warning lights?????????????
Ant ideas would be welcome.

Geoff Shine, October 2010

The alternator may not be hearthed properly to the battery check all the connections to and from it.

robby, October 2010

Many alternator voltage regulators are today linked to the vehicle's onboard computer system, and in recent years other factors including air temperature (obtained from the mass air flow sensor in many cases) and engine load are considered in adjusting the battery charging voltage supplied by the alternator.

Peccavi, October 2010