With the appliance unplugged you will need multimeter to check resistence of heater to confirm its failure.
As for diagrams may I refer you to top of this forum namely...Professional Advice in the Public Forums
Penguin45 wrote:Advice in Public Forums.
8/ Please do not ask for wiring diagrams, schematics or for us to sort out any wiring problems over the internet. We cannot judge how competent you are nor the future readers of any thread, we'll try to point you in the right direction but that's as far as we can legally go.