It's inside the lower cover if it's anything like my 100e.
Remove lower plastic cover by undoing captive screw underneath and behind flap and slide cover off forward.
Remove securing screw of electrical carrier plate and lower it down. P Switch towards the rear on right of PCB enclosure - air pipes going to it - sometimes possible to repair it so I've read on here.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.