Nissan Primera P12 electric problem

check wiring from alternator. is it bright or dim?

The regulator is inside the alternator on all the cars I've looked at in the last 20 yrs so I guess the P12 is the same.

Has anyone changed the bulb?  The wrong wattage bulb might throw the regulator off beam as the bulb is part of the feedback circuit to the regulator, reducing charge and the light then stays on, but I think you would still see the brightness dim a bit with the engine running. 

If it's bright and doesn't change then the obvious fault is that the new alternator has no output. 

As for wiring, it's difficult to see what could be broken as if the bulb weren't connected it wouldn't light up so that accounts for the thinnest wire to the alternator.  The 2 fattest wires should have 0v and 12v on them from the battery via fuses.  I just thought of one fault that may cause your problem though and that's a short circuit from the thin wire at the alternator to chassis, you would have to disconnect the battery to test for that on a DVM on the lowest resistance range.

had a meter on battery its fully charged,when car running its over charging.

many thanks 2 steveb and kensai86.some one checking it for me later will let you no.

Hi there and a big welcome to NPOC