headlights not working

[kevow]

when operating light switch , main beam headlights do not come on

[woodchopper]

Bulbs blown - switch faulty - fuse blown. Take yor pick.

[Panic Button]

Does headlamp flash still work? That would eliminate the bulbs being blown.

If not then you are still down to the switch or a fuse.

Sometimes a different fuse covers the left and right, which makes the switch the suspect

[mr rusty]

As well as the fuses, if it's a fairly modern car there will also be a relay or two involved- really you need to check your manual for the fuses you need to look at, and also the relays.