1989 Plymouth Acclaim, 2.5 liter. The radiator cooling fan relay clicks continously when the engine is running but the engine and coolant are cold. The fan moves just slightly each time. This continues until the relay fails. The relay and fan work properly when the coolant reaches the level where the fan comes on. Have replaced thermostat, coolant temp sensor. Radiator is full. Doesn't use coolant or oil. What can cause the clicking? Temp control is not set to air or defrost.