Perhaps the simplest test could be to select ohms on your meter and check that you have a resistance across the two wires going to the indicator lamp holder with the lamp in place..? If not with the meter still connected try removing and replacing the bulb and see if it the reading alters...
Another posibility is to connect a 12 volt supply across the same two wires to see if the indicator lamp lights up.. and if not, with the 12 volts still connected again try removing and replacing the lamp, if it flickers and fails to stay lit during the replacement process then you may have a corroded bulb holder connection... either live, earth, or both.
Of course the earths ever tend to be the prime suspect and a cruddy lamp cap can be cleaned up with a rub of steel wool to testore connection to the metal of the lampholder where it picks up it`s earth.
Sometimes the lead contact on the centre of the lamp cruds up, or that which it connects to in the centre of the lamp holder, where a scrape with the blade of a screwdriver can restore connectivity...
Good luck Peter, you will get there.
