Cromartie Hobby 20 kiln control switch

I have been given a Cromartie hobby 20 kiln and i have a problem that I
think is with the control switch. Can anyone help?
When I have fired the kiln with a 0.3 Orton cone the cone has not distorted
enough to turn the kiln off, even after 27 hours. When using the 0.5 cone
it has switched itself off on the two occasions that I have tried it.
I have taken the control switch out and can see that it has an adjustment
knob on it. Can anyone suggest how this works ie which way should it be
turned and how far. It may just be a case of trial and error but any advice
would be appreciated. I am reluctant to buy a new switch as I am not
entirely sure that it is the switch that is the problem.
You may have gathered that I am completely new to pottery and this is very
much a trial and error project for me. Thanks for any help that can be
offered.