Before thinking it's a bad switch, test the connection with a meter. I suspect it's only corrosion.
It is a not a great lamp and it is subjected to lots to water splash and is not really waterproof, barely water resistant.
I did as the previous poster and put in a 36 LED panel, much better light, I also greased the connector with dielectric grease. Works fine now.
Ideally a marine grade lamp would be best, but these are not cheap, and truth be told, I have rarely used it...
Denis & Diane
2010 Sabre 31REDS
Ford F-250 2011
* Happy Campers *