I posted pictures on the location and replacement of an ambient temp. sensor for a 2001 S40. Google "ambient temperature sensor location/replacement" or go to Matthew's Volvo site and search there.
Next to the thermostat. you will see it when you remove the hose
If you mean for Coolant level sensor it is on the bottom of the plastic coolant dish on the passenger side of the car.
I'm not sure what you're asking, but if you mean that you are getting an OBD-II diagnostic code of P0128 from your Volvo S40, that code corresponds to a problem with coolant temperature. On a first generation Volvo s40 (99-04), this usually means that the thermostat or electronic coolant temperature sensor are malfuctioning or have failed.
In a 1993 Volvo 940, the block temperature sensor is typically located on the engine block, near the thermostat housing. It can be found on the driver's side of the engine, often near the cylinder head. This sensor monitors the engine's coolant temperature and sends the information to the gauge on the dashboard. If you're having trouble locating it, consult your vehicle's repair manual for a detailed diagram.
in mirror
On the passenger side of the engine compartment there is a surge tank remove that and the sensor is in the bottom. It will be the clear plastic tank where you add Coolant.
On my 2000 International with a Detroit series 60 engine the water temperature sensor is on the back of the engine, passenger side in the cylinder head. Gears
it's on the radiator, just pull the wires and unscrew it.
My 2002 has it in the drivers side mirror.
Usually right above your temperature control on your dash
driver side