My 1996 2.5 V6 Sebring convertible's radiator fan is cycling on an off when the AC is on for about 20 seconds, on and off over an over. I know it is supposed to run when the A/C is on or if the temperature rises. My wife's PT Cruiser does the same , but hers runs about 1 minute cycles. On an off. I know the system is working, but the short cycles make me think that something could be malfunctioning. Any suggestions?