This is a common problem on these switches, MMC in their wisdom didn't fit headlamp relays, so the switch contacts take the full current and burn out.
The correct switch is a Triumph part, and they are expensive. you also have to bend the arm in 2 places to get it to fit, which is a bit of a trepidatious experience when you've just forked out 75 quid on the thing.
When you get a replacement, do yourself a big favour and fit a pair of relays to save it happening again. There's a set of instructions on how to do it on Morganatica:
https://sites.google.com/site/morganatic...m-switch-repair
