you are correct, that trouble shooting with the fan is a good way to test for other stuff misbehaving too.
There are 3 things that can be causing the TV to behave this way:
1- A bad lamp: which you say you have replaced, make sure it was not a generic lamp! Non OEM lamps have a high defect rate and you could have gotten a DOA, or defective lamp. Buy Philips bulbs, the model for this TV is UX21515.
2 the ballast, if its old enough it might not be strong enough to power on the new lamp.. an arching sound comes out of this part when it malfunctions sometimes. If it fails to ignite.
3- the colorwheel can be cutting the power to the ballast out.. I do not think it is this part for it could have given you some color distortions.. a whirling bearing or grinding sounds comes of this..
I am not sure where the temp sensor is but it should not look all that different from the one you found online and placed nearby the lamp for it is one of the hottest components aside from where it focuses on..
Hope this helps