Jaguar Repair: Battery charging, belt tension, voltage meter

Question
On my '87 xj6 I recently replaced the battery and about a week later the red battery light came on and noticed the voltage meter had dropped from the normal (around 13) to just above the red zone.  A few days later the engine died and wouldn't restart, but was able to jump it, but then died again.  Put a new battery in and now have the same readings, but the warning light is flickering and will go out occasionally.  Any ideas or suggestions?

Answer
Hi Bob,
You need to first check the belt tension and then check the connections from the alternator to the battery and the exciter wire to the instrument cluster where it is connected to the charge light and a jumper resistor. Also check the grounds from the engine to the frame and from the body to the battery.

If all that is ok put a volt meter across the posts of the battery and read battery voltage (12+ volts) and then start the engine and run the RPM up to about 1200 RPM and read the voltage. It should read from 13.8 to 14.5 volts. If it don't you have a faulty alternator and/or regulator. (the regulator is inside the alt.)
Howard