Iat Sensor.
Engine Coolant Temperature Sensor.

IAT SENSOR

Fits 850, 940, 940 SE, 960, C70, S70, S90, V70, V70 XC, V90

Engine Coolant Temperature Sensor
If your engine coolant temperature sensor has failed, you may notice one of several symptoms: your temperature gauge doesn’t move, your engine overheats without warning, your radiator fans don’t switch on, or they don’t switch off. If your 2005 Volvo V70 has any of these symptoms, it's a good idea to let a trained Volvo technician perform an inspection.