Hi Kandlbarrett, thanks for your guidance. I am looking forward to do the drop test tomorrow. I am confident that the audio guy that I'm going to will be able to identify the issue - be it the battery, alternator, radiator fan or the wiring. To be honest, I have seen exposed copper on the insulation nearest the radiator fan connectors. I'll get him to have a look at that too as a possibility.
Actually I have made another observation:
The other time, when I did the test or revving the engine at 3K rpm until the fan activated, the engine had started from cold as it had been standing for a few hours prior.
Drive my car for the past 2 days, what I have observed is, in the beginning, the voltage is good(around 14V) but, once it has warmed up to operating temperature, and I have either the head lights, hi-fi or a/c turned on, when I step on the brakes to come to complete stop at junctions or traffic lights, the voltage actually dips to 13.2 - 13.4 V and then stabilises to around 13.6-13.7 V. This is when the issue starts to happen.
After that has happened however, if I turn it all off (headlight/air con/hi-fi) and keep revs above 2500RPM the voltage starts to stabilise at 13.8 - 13.9 V and the problem seems to go away.
In the mornings on the way to work, if I do not turn on any of those, I can actually make the 26km/16mile journey without the voltage dropping below 13.9 V and so, without the engine stumbling.
I really appreciate everyone's feedback on this matter so far without which, I don't think I would be heading in the right direction in trying to find the source of this issue.
To be honest, when the issue started initially, I had tried approaching a couple of 'automotive electronic' shops in Singapore to get them to have a look at my car. But nobody seems to want to touch an Alfa with electrical issues.
I even had 2 friends who, like me, drove 147s and had electrical issues that they couldn't resolve and, had to surrender and scrap their cars. I just hope that my car doesn't end up as a statistic.
Once again. Thanks all!