Battery light

Hi guys , today my battery light come on and rev counter stopped working so put volt meter on the alternator and it was charging so cleaned the terminals but still the same so took one off a spare vehicle .. Everything is ok now apart from when I turn the ignition on I don't have a battery light on , I have my hand brake,oil and heater plugs but no battery light .. Any ideas guys ???????

Went to start her this morning and I had a battery light once started it went out as it should but switched off and tried again no light after that :-( wtf ... Any ideas guys ??? Is it the alternator AGAIN ?

i had that follow the excitor wire back from the altenator and make sure the wiring has not melted (the outer sheath) mine was shorting out just by the head