Volkswagen Golf/Jetta 2 manual

Cooling system electrical switches - removal, testing and refitting
Cooling, heating and air conditioning systems / Cooling system electrical switches - removal, testing and refitting


Cooling fan motor thermoswitch 1 Disconnect the battery negative lead.

2 Drain the cooling system.

3 Unscrew the thermo-switch from the left-hand side of the radiator and remove the sealing ring (see illustration). Note that from September 1985, on fuel injection engines (except 16V) the switch, located in the bottom of the radiator, is of a 3-pin type, replacing the previous 2-pin type. The new switch has two operation temperature ranges, the first range operating the coolant fan at normal speed and the second range operating the fan at boost speed.

7.3 Cooling fan thermo-switch
7.3 Cooling fan thermo-switch

4 To test the thermo-switch, suspend it with a piece of string so that its element is immersed in a container of water. Connect the thermo-switch in series with a 12 volt test lamp and battery. Gradually heat the water and note its temperature with a thermometer.

The test lamp should light up at the specified switch-on temperature and go out at the specified switch-off temperature. If not, renew the thermo-switch.

5 Refitting is a reversal of removal. Fit a new sealing ring and tighten the thermo-switch to the specified torque.

6 On completion, refill the cooling system.

Cooling fan temperature sensor 7 From March 1986, the cooling fan is also controlled by a temperature sensor located between injectors 1 and 2. A time relay is also incorporated in the wiring circuit to keep the system functional for 10 to 12 minutes after switching off the ignition.

Temperature sender
unit/thermo-switches
8 It is not necessary to drain the cooling system if some form of plug, such as an old sender unit or rubber plug, is available as a substitute for the removed switch.

9 Release any pressure in the system by unscrewing the pressure cap. If the system is still hot, observe the precautions at the start of this Chapter. With all pressure released, retighten the cap.

10 The location of the sender unit or thermo-switch is dependent on engine type.

In general, they are as follows: 1.05 and 1.3 litre engines 11 The thermo-switch is located in the intermediate piece in the hoses between the inlet manifold and thermostat housing (see illustration).

7.11 Temperature sender unit thermoswitch location - 1.05 and 1.3 litre
7.11 Temperature sender unit thermoswitch location - 1.05 and 1.3 litre

12 The temperature sensor is located in the thermostat housing (see illustration).

7.12 Temperature sensor (arrowed) - 1.05 and 1.3 litre
7.12 Temperature sensor (arrowed) - 1.05 and 1.3 litre

1.6 and 1.8 litre carburettor engines 13 The temperature sender unit is located in the heat exchanger hose connecting flange on the rear of the cylinder head.

14 The thermo-switch (inlet manifold preheater) is located on the top face of the hose connector on the spark plug side of the cylinder head.

15 The thermo-switch (automatic choke) is located in the base of the hose connector on the spark plug side of the cylinder head.

1.8 litre fuel injection engine 16 The temperature sender unit is located in the hose connector on the spark plug side of the cylinder head (see illustration).

7.16 Temperature sender unit (A) and thermo-switch (B) - 1.8 litre, fuel
7.16 Temperature sender unit (A) and thermo-switch (B) - 1.8 litre, fuel injection

17 The thermo-switch is located on the top face of the hose connector on the spark plug side of the cylinder head.

1.8 litre 16V engine
18 The temperature sender is located on the flywheel end of the cylinder block below the outlet elbow and controls the temperature gauge.

All engines
19 Disconnect the wiring lead from the sender unit/switch concerned.

20 Unscrew and remove the sender unit/switch and plug the aperture.

21 Refitting is the reversal of the removal procedure. Tighten the sender unit/thermoswitch to the specified torque.

22 On completion, check and if necessary top-up the cooling system.


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