Electric shower wont switch on?

I have a redring expression 500s 18mthsw old . It just stopped in the middle of a shower. There is power getting to it. I have checked the on off switch on the shower with my meter. It operates. There is power getting to the both sides of the thermal cutout on top. There seems to be a slight burning smell at the connection of the 2 brown heavy wires and the 2 small wires at the bottom of the shower connected along side the on off switch. What is this for or could it be the problem