oil warning light

[Foxhill]

Noticed that there is no oil light bulb fitted to my 1990 2.4 surf. Swapped the battery warning bulb into the empty slot but didnt light up on start. i have an oil pressure gauge that works fine so can i leave things alone and just keep monitoring the gauge or should i fit a new engine oil switch and new bulb?
Is the engine switch a 2 part switch that does the gauge and warning light, would i need a complete unit or just one section?
Any thoughts appreciated. Neil

[BUSHWHACKER]

To see if the bulb lights up.......
The next time you do an oil change, drain the engine oil, then switch on ignition. The light should come on as I think it is a low oil level light rather than a pressure warning one.