Execution order
1. If the electric fan does not turn on at a coolant temperature of 93–98°C, then it is most likely that the electric fan switch sensor has failed. To check the sensor, disconnect the wires from it and short-circuit them directly; the fan should turn on even when the ignition is off. This indicates that the sensor is faulty and needs to be replaced.
2. Before replacing the sensor, disconnect the wire from the negative terminal of the battery. Drain the coolant (see paragraphs 1–3 of subsection 4.1). Unscrew the sensor (16) (see Fig. Cooling system of a four-cylinder engine) or (19) (see fig. Cooling system of a five-cylinder engine) from the radiator, disconnecting the wires from it. Remove the gasket. Install the sensor in the reverse order, while replacing the gasket.
3. To check the removed sensor, connect the battery and a 12 V lamp in series with the sensor. Immerse the threaded part of the sensor in water and heat it. The sensor should turn on the lamp at 93–98°C. Then let the water cool. At 88–93°C, the sensor should open the circuit and the lamp will go out. If the sensor response temperatures do not fit within the specified limits, then it is faulty and must be replaced.