This may apply to other models too.
Projector turns on, you hear the fan for a short while, then it powers off. Power light then flashes Orange and Lamp light is steady Red.
Dirty light sensor - means sensor can not detect enough light and thinks lamp is dud and turns itself off.
Take out lamp.
Unscrew case - 2 on bottom - 2 on back.
Then you have to prise off the lid - a very thin screwdriver inserted in the edges and pushed along works - don't force it too hard - but eventually it clips off.
DO NOT lift the lid up too far as there is a ribbon to the buttons - if either end snaps off/pulls out they're a pain to refit and you may lose the tiny brown ribbon clips - that secure the ribbons. (I think they normally lift up).
There's enough room to get a cotton bud around the square light sensor.
You can test while lid lose but have to have lamp in with its cover.
Refit in reverse.