Examination
Note: To check the functionality you will need an ohmmeter.
1. The sensor performs two functions. A resistor with a negative temperature coefficient informs the control unit of the heating system about the temperature of the coolant, and the switch interrupts the power supply to the exhaust gas recirculation solenoid valve. The sensor must first be removed as described below in steps 7-9 and then it can be tested.
2. Connect an ohmmeter to pins 1 and 4 of the sensor connector. At room temperature, the resistance should be infinite, i.e. the thermal switch contacts are open.
3. Then tie a string to the sensor and lower it into a container of water (it should not touch the walls or bottom of the container). Place the thermometer in the water and begin heating it. Check that the thermal switch contacts remain open at 20°C and close at 30°C. When the contacts are closed, the ohmmeter should show zero resistance.
4. Connect an ohmmeter to terminals 2 and 3 of the switch. Heat the water and check that the thermistor resistance is (coolant temperature sensor) is in accordance with the data given in Specifications.
5. If the results obtained are unsatisfactory, the switch is faulty and must be replaced.
Removal
Warning: Remove the temperature sensor only from a cold engine.
6. The sensor is attached to the thermostat housing, on the left side of the cylinder head. It has a black electrical connector.
7. Drain the cooling system as described in Section 1. Alternatively, prepare a new sensor or a suitable plug to quickly seal the hole and prevent fluid from leaking.
8. Disconnect the electrical connector, then unscrew the sensor. Remove the O-ring.
Installation
9. Install in reverse order, using a new O-ring.
10. Finally, fill and bleed the cooling system as described in Section 1.