I have a 99' pontiac grand prix GT3.8L, My car overheats when it sits at a red light,I have changed the radiator,All relays,thermostat,rad.cap,temp sensor, waterpump bled system,there is three wires that go to the temp sensor I cut the yellow wire and the fans kick on also the fans do come on when a/c is on Please help!

Welcome to AF.

It would help to post what engine you have.

he did if you look its a 3.8 and in a 99 gt that means a natural series 2

it only runs hot at idle or does it o/h in other situations

he did if you look its a 3.8 and in a 99 gt that means a natural series 2

He edited his post to update that information at my request. Are you blind?

BTW - That is normally aspirated aka na Series II.

I have a 99' pontiac grand prix GT3.8L, My car overheats when it sits at a red light

define overheats. does it boil over? steam? smell like antifreeze? or are you just going by the temp guage? and how hot does the guage get when it over heats?

I have a 99' pontiac grand prix GT3.8L, My car overheats when it sits at a red light,I have changed the radiator,All relays,thermostat,rad.cap,temp sensor, waterpump bled system,there is three wires that go to the temp sensor I cut the yellow wire and the fans kick on also the fans do come on when a/c is on Please help!

I'm assuming you checked your oil and it is not milky white in color. Have you checked the radiator to see if you have a head gasket leak? Pretty easy. Two ways:
Look to see if your coolant bottle is over-filled. If it's not then with the car cold, fire up the engine, take the radiator cap off and check to see if you have bubbles coming to the surface of the coolant. The other thing to do is goose the throttle at the throttle body and observe if the coolant is pushed out the radiator while the car is still running cold. If it does push the water out more than likely you have an exhaust leak in the cooling system. Same goes for the bubbles if you see em. I've seen em the size of pin heads rising to the surface and bigger.
Don't forget to bleed your system after you put your radiator cap back on.