Cooling fan works but not kicking in when engine gets HOT

I do have one question I hope you can assist me with,

Having checked the fuses (all OK), I hard wired the cooling fan to the battery (fan works), checked the two relays (cleaned and checked, OK), drained, flushed and filled the radiator and engine cooling system (new antifreeze and water) AND removed and tested the thermostat in a pot of boiling water (opened and closed OK),

The only thing left that I can think of that may be the issue is/are the temperature sensor/s, unfortunately I didn’t get to remove them to get the make and model number, from what I saw and according to the manual there are two, one located below the thermostat on the side of the engine block and one leading into the thermostat one green one blue.

Is there any possibility that you could please let me know what would be the correct make and or part number for both of these sensors

and

if there is any way of testing them with a multimeter.

Many Thanks