Battery / alternator woes a comming?

Well it sounds like the alternator is charging reasonably well- when you mentiuon the light coming on when you go through a puddle, that is probably water on the drive belt causing it to slip, however i would get a voltmeter on the battery to be suire and check carefully for corroded connections- not just at the battery- the earth strap and engine block earths as well as the alternator connections. With engine running at fast tick over and lights / fan blower / HRW etc on you should still see upwards of 13.2v at the battery. Any less and the battery is never going to be fully charged.

sencondly what Ah battery have you got? It sounds like its not a big enough capacity for the diesel engine- the petrol perhaps... A good rule is the biggest (i.e. highest Ah) one you canb fit on the tray, never mind what is said as "adequate".

Tim..

Will do!.............. in the light!

Well the new battery of last November is a bigger capacity than the old bog std vaux batt....which as i recall the old one, (which to my eyes didnt seem knackard to start with, but the guys toaster type thing told him it was)

One thing i do notice is when i put the hazards on and if i have to door open the interior light dims and brightens as the flashers flash

You may well want to start bt checking the terminals on the battery. Clean them up & refit them & then check the other end of the negative lead to the body work & the engine earth to body work. Fixing that's free. After that you want a cheap multimeter, measure voltage with engine running, voltage without engine running, voltage without engine running & lights on & voltage when starting engine. That'll give you a good idea what's faulty for a fiver down Maplin

I'd also check the tightness on that alternator drive belt, if it's slipping when wet, it may be slipping under load too, but not enough to bring the charge light on.