The radiator fan starts when the cooling system reaches a certain temperature. A double temperature switch operates in two temperature ranges, in the first temperature range the low fan setting is activated and in the second temperature range the high setting.
If the switch, which is mounted in the radiator, does not pass any value, the fan will either not start or will only operate at one setting, depending on the temperature range of the defective switch.
If the motor temperature rises, or cannot reach the temperature at which the fan does not run or only runs at one setting, the switch is most likely broken and must be replaced.
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