tempature

[alprotege]

i installed a ac autotechnic reverse glow temp gauge and the i dont know if the gauge is reading the right temp. i had to buy a adapter for the temp sensor to fit because it was to small for the factory hole in the block, so the adapter fit inline with the top radiator hose and the gauge is reading about 140-145 degrees, i think our thermostat is a 180 but the guy at the local autozone told me that putting it there would make it read about that much different in temp, i guess because it has time to cool through the radiator before it gets back to the sensor. any truth to this? thanks.