karcher k2

Hi, I have a K2 pressure washer and need to change the power 'on/off' switch. I have bought a new switch but can't seem to fit the switch into its retaining housing as it seems it can't fit over the 'white' plastic protrusion (see attached photos). The swich should just 'click' into place but...

My K2 Compact stopped working after a couple of minutes. It is 4 year old. I have been reading different posts and I believe it is not a capacitor. It also smells like burnt. When I opened it I found that 2 plates were missing. So I believe that is the reason why I only get a buzzing noise but...