Just wondering what type and size wire to use for the little switches that activate the interior lamp on a ute when the door opens? I have a bunch of spare wires lying around from other things I ripped out....audio wire, bits from a spotlight, and other bits for tow bar/trailer light interface. Is there anyway to measure wire guage? Thanks.

Automotive wire should always be stranded. Best to use (or re-use) wire made specifically for it as it has the correct properties and insulation. You can buy small rolls of it at the local autoparts places like Repocheap.

The gauge is small probably 16 or 18.

Speaker wire might be OK.

Thanks DD, guess you are right, I should just go buy some new.

Spot light stuff will b to big well if spot lights were fitted right, u can still use but overkill, as for speaker wire its not as good as power wire as it's ment for small responsive signal and does heat up if u run constant power through it! If u have trailer plug wire or harness wire thats perfact, but you could always go buy some new from jaycar or supershit, ect or go see your local auto elec for some!