Thats what i was trying to ask

Right, not very easy to see, but you need to look at the alternator wiring.

Theres a thick red wire, and a thinner wire (i dont know the colour)

The thinner wire is the wire we are interested in. There are 2 terminals it could connect onto, have a look at which one its connected to.

Then you could try disconnecting the wire and doing a simple test.