Electric cooling fan thermal switch
1. Be guided Chapter 10 from this Section for a quick test that should identify faulty switches.
2. To perform a complete test, the switch must first be removed from the radiator as follows: First, disconnect the switch wires and check that the engine and radiator are completely cold.
Figure 2.12. Thermostat testing
3. To prevent leaks, drain a small amount of coolant or remove the radiator cap to release residual pressure.
4. On vertical flow radiators, unscrew the switch from the radiator and quickly plug the hole with a plug; be careful not to damage the radiator, and do not use anything that may leave pieces inside the cooling system. When installing, apply a suitable sealant to the threads of the switch, tighten it securely. Check the coolant level, top up if necessary, as described in Chapter 2.
5. On cross flow radiators, turn the switch lock one and a quarter turn counterclockwise and remove it from the radiator housing (photo), then remove the switch and discard the rubber seal. Plug the hole. Installation is the reverse of removal, always use a new seal.
12.5 On a cross flow radiator, remove the cap from the thermal switch
6. To test the switch, connect an ohmmeter and lower the switch into a tray of heating water (figure 2.13). Measure the water temperature with a thermometer. Make sure that the switch or thermometer does not touch the tray.
Figure 2.13. Checking the thermal switch of the electric cooling fan
Figure 2.14. Checking the water temperature sensor - fuel injection models
7. The switch contacts should close when the water heats up to the specified temperature. Turn off the heater and let the water cool down. The switch should open when the water cools down to the specified temperature.
8. Note that switch #1 is installed on the right side of the radiator (from above or below) and controls the fan motor via one or more fan motor relays. Switch #2 is only installed on models with a two-speed main fan motor; it is screwed on the top left side of the radiator.
9. If the switch does not fit within the specified temperatures, it must be replaced.
10. Note that on carburetor and Turbo models there is a connection from the switch to the idle mode system (Section 3).
Coolant temperature sensor (thermal transmitter)
11. The coolant temperature gauge installed in the instrument panel is controlled by a sensor (referred to as a heat transmitter in electrical wiring diagrams) which is screwed into the intake manifold behind the thermostat (photo).
12.11. A Coolant temperature indicator sensor - carburetor models
12.11B Coolant Temperature Indicator Sensor - 2.0L Fuel Injected Models
12. The sensor contains a thermistor, whose electrical resistance decreases according to a certain law as the temperature increases.
13. To quickly check the circuit, turn on the ignition, disconnect the sensor wire and short it to the engine; the temperature gauge arrow should move to the maximum position "Hot" and return to the position "Cold" if the wire is disconnected from the ground, if the gauge behaves as described, the sensor may be faulty and should be checked; if not, there is damage to the indicator or wiring.
14. To check the sensor, unscrew it from the manifold. Plug the hole to prevent refrigerant from leaking out.
15. Connect an ohmmeter between the sensor clamp and the sensor body, heat the water and measure the resistance as the temperature rises. Compare the results with the value in the Specifications.
16. If the results differ, the sensor must be replaced.
17. When installing, apply sealant to the sensor thread, carefully tighten it with the specified tightening force Specification. Check the coolant level, top up if necessary; see Chapter 2 of this Section.
Water Temperature Switch - Automatic Transmission
18. All cars with a carburetor and automatic transmission are equipped with a separate thermal switch, which is screwed into the intake manifold behind the thermostat.
19. Removal and installation are similar to the procedures described in points 14 and 17 above.
20. To test the switch, proceed as described in step 6 above. The switch contacts should close at approximately normal coolant operating temperature.
21. If the switch is faulty, it must be replaced.
Water Temperature Gauge - Turbo and 2.0i GSX Models
22. To control the engine temperature, the control unit receives a signal from the temperature sensor, which is screwed into the thermostat housing (photo). The unit is controlled by the coolant temperature.
12.22. Disconnecting the temperature sensor - 2.0L models with fuel injection
23. The sensor contains a thermistor, the electrical resistance of which decreases according to a certain law as the temperature increases.
24. Remove and install the sensor as described in points 14 and 17 above (photo).
25 To quickly check the sensor, disconnect the wires, measure the resistance at the sensor terminals on a completely cold engine. Reconnect the sensor, start the engine, warm it up to normal operating temperature. Stop the engine, disconnect the sensor wires and measure the resistance again; the resistance should be much lower and correspond to the values specified in the Specifications.
12.24. Removing the temperature sensor of the 2.0L model with fuel injection
26. To fully test the sensor, remove it and connect a multimeter across the clamps, then lower the sensor into a tray of heating water (figure 2.14). Using a thermometer, monitor the temperature, do not allow the sensor or thermometer to touch the tray. As the water heats up, note the corresponding resistance data and compare them with those specified in Specifications.
27. If the sensor is faulty, replace it.