Radiator Fan Switch: Insight

Remove radiator fan switch from thermostat cover. Suspend switch in a container of water without it touching the sides or bottom of the container. Insert thermometer in container without touching bottom of container, and heat water. Measure continuity across radiator fan switch terminals. When temperature of water in container is 201-208°F (94-98°C), continuity should exist across radiator fan switch terminals. Allow temperature of water in container to cool down. When temperature drops 5-15°F (3-8°C), continuity should not exist across radiator fan switch terminals. If switch does not test as specified, replace radiator fan switch. Bleed air from cooling system after installing radiator fan switch in thermostat cover. See SPECIFICATIONS article in ENGINE COOLING.