One of the more common faults on Mk1 Fabias and similar is the breakage a couple of thin wires going to/from the alternator. There are hundreds of threads on this forum about these problems, here's a link to a fairly recent one: http://www.briskoda.net/forums/topic/287467-load-signal-alternator-cable/   If the blue wire breaks, the alternator won't reliably start up and may only start up at higher revs, leading to low-voltage/battery problems.  Another thing that happens when the