If the lights are dimming when you turn the key all the way on then it sounds like it's trying to get the starter working but something between the switch and the starter isn't right. When you bypass the switch to start the car are you doing it by shorting out the relay on the starter with something metal or are you connecting a wire from the battery to the starter relay?
If you're not using a wire try it that way. This will tell you if the starter relay has a problem or the switch.
Let us know how you go.
Cheers
Paul
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