Can anyone help with some advise and info please, I have a problem with my 96 Galaxy 1.9 TDi showing battery/charging light constantly on while engine running. Problem started with speedo behaving erratically, followed next morning by a dead battery. after a new battery fitted all the instruments on the dash now behaving erratic (dash back lights flashing on/off, needles flicking up and down) but more so the speedo needle (around the clock and back again constant changing). changed the speed sensor unit underneath the car on back of gearbox and initially no change, but while test driving the car after changing it and after turning on full lights and heated front and rear switches the sdials corrected themselves back to normal!, but i now have a constant red battery light showing while running. Have checked the battery with meter and it shows 12.1 volts engine off, 12.3 volts on idle rising to 12.6 volts higher revs and down to 11.8 volts with all heated circuits and lights on. can also fluctuate up and down between these while reving and under load. Am i looking at internal fault in alternator (are they servicable?) or complete new alternator unit? Im also looking at replacing the drivebelt tensioner as i seem to have the dreaded noise from under the bonnet and the belt is jumping up and down at idle. Your help would be much appreciated. Thanks