The voltage on my laptop display whilst monitoring the MS ECU seems very erratic...
Ive just fitted a new alternator as the old one was dropping to 11.7v under heavy load (according to the laptop) when i first fitted the new alternator at the weekend the Voltage read 13.9, went for a drive yesterday and it was 12.7 - 12.9 fluctuating... No extra electrical load.

Now im going to test it with a multimeter tonight, but in the meantime am i right in thinking the ECU probably isnt a very accurate voltmeter and not be too worried or should i presume the alternator is already dying...?