I've seen similar issues on the Navara forums where people are saying its a fault with the alternator or the alternator pully (forgive me if I've got that wrong) but without a manual I'm a little lost as to where to start looking. I do also have a squeal sometimes when I start the car and a mechanic once said to me that it sounds like the alternator belt might need changing. Again I have no clue where I am looking or even how to check if it's the belt or not.
I've got a multimeter for checking the charge, etc if needed, just wondering if anyone else has had a similar problem to guide me where to look first (and as cheaply as possible

TIA for any help.