Pontiac Repair: 99 Bonneville High Temperature, coolant leaks, temp guage

Question
Sorry for the length. I’m having a problem with the over heating or indicating it’s running hot in traffic. It cools right down once I able to start moving again. Naturally I check the cooling fans which are both working, Thermostat has been replace, Water pump producing good flow looking through the radiator cap, No coolant leaks; that I can find and have recently flushed the cooling system and transmission. Radiator has Transmission feed also.
Recently had to replace the pressure sensor on the Air Conditioning Compressor due to a false high, what’s the probability of getting false reading from the Engine Tempter sensor and how can I verify it ?  

Answer
ok well first off you can getr a mechanical gauge and compare it to the temp guage or light on your vehicle, if the front of the radiator is blocked with grass and or debri it will cause this as well, or if the a/c system in builidng to much temp if front od the rad it will cause the heat transfer to the radiator, doe it get hot with the a/c off? on? are the cooling fans operating at the speeds they should or are the weak and slower? the re are manyhting that can cause this i hope this helps