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Radiator Cooling Fan After-Run System

Many of the models covered by this manual are equipped with the radiator cooling fan after-run system. Information about the radiator cooling fan after-run system for a specific model can be found in CURRENT FLOW DIAGRAMS. 1985 through 1987 models can be retrofitted with the system using a kit which is available from your authorized Volkswagen dealer Parts Department.

The system uses a cylinder head mounted thermoswitch (as shown in Fig. 4-10) to sense excessive engine compartment temperature. High temperature closes the switch, making a ground connection for the after-run control unit and operating the cooling fan for up to 15 minutes. The control unit is located on the fuse/relay panel.

Test the system, with the ignition off, by disconnecting the black wire from the thermoswitch and grounding it. The thermoswitch is mounted near the top of the engine, behind the cylinder head cover, between no.2 and no.3 cylinders. The fan should run on low speed. If not, check for battery voltage (approx. 12 V) from the control unit (terminal 8/87) to the fan (terminal no.2, red/white or gray/black wire). If there is no voltage from the control unit, it is faulty and should be replaced.

If, with the thermoswitch connected normally, the fan runs continuously (more than 15 minutes), disconnect the black wire from the thermoswitch. If the fan stops, the thermoswitch is faulty, permanently shorted to ground, and should be replaced. If the fan continues running with the wire detached, the control unit is faulty and should be replaced.

Fig. 4-10. Radiator cooling fan after-run thermoswitch on cylinder head senses high engine compartment temperature.

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