I recently got a Mark3, 1.6, 1998 Arctic model(AC and PAS) - low mileage. After working flawlessly, starting even in extreme cold spells, it suddenly refused to start after a short run. Battery flat (how??). Then it started OK after 20 minutes. Next time battery flat. Not the usual slow death. Can be booster started. PAS no trouble.
The break-down man said possible intermittently faulty alternator - was not sure though. Battery fine and the Alternator (Delphi) looks new, belt not slipping.
No faults displayed.
I am planning to get another Alternator and belt anyway as backup, have HAYNES.
However, as I know a bit about circuits, I think there may be another fault. When the car is started the battery 12V drops to 11.5. Only When revved the Alternator comes in to play and voltage is boosted to 14.5V. I think, PLEASE CONFIRM, the alternator charges the battery via some relay or something. It is too cold to play with a multimeter at the moment, so any quick pointers/solutions will be most useful.
Also I dont need AC so can I simplify the belt drive with a different belt? Part no?
Many thanks for this great forum