my battery light doesn't illuminate... hasn't for years

when i first start the car the secs shows around 12volts with the enigne running. after ONE rev to 3/4k revs te alternator kicks in and i get a healthy 13.7 volts...

the mot tester mentioned that the battery light not working causes this need for a rev to start the car charging...

any thoughts on this?

is the battery light just a push in bulb or is it not a simple as that ie soldered in place or something?

cheers!

 

its a turn fit bulb into the dash board. but check the thin blue wire to the alternator is ok and connected properly.

 

as said its just a bulb, its the blue wire from the alt going to the bulb in the clock then onot a switched live to turn the alternator on to charge the car

turn all lights and heaters on and rev the car and check the voltage drop at the battery

 

Just take the blue wire off, and whilts running tap a LIVE onto the alternator terminal(IND) from where the blue wire came, this will start the charge, if it does most likely just a bulb, this terminal is negative when engine stopped, but changes to positive when running extinguishing light.
As said bulb controls the start of charge by exciting field windings in alternator.
tabetha