David and Group, I now have two different otterstats to turn on and off at about 10 degree F different depending if you live in a cooler climate and want it to turn on less such as David or in the southern hotter climate such as me and want the fans to turn on sooner. I have both described on the web site at http://www.specialtauto.com/engine.shtml, At the point on the gauge where Davids is turning on is where mine turn on with the cooler unit 92c x 2.13 = 196F and the 97c x 2.13 = 207F. When I install the hotter, unit my gauge is about 1/8th above the 160 / 2nd mark. The otterstat is turned on by the temp of the coolant, since there should be no air in the line because he has a air bleeder, then it would be resonable to expect that maby the Circuit breaker is heating up and turning the fans on and off . The only other thing I can think of would be air getting in the line continuiously like another was doing earlier. A friend of mine found out he had a leaking head gasket and another reported air was leaking in around the otterstat. David, It's a good question. I would maby opt for air getting in the line as fast as it's bleeding out. Naturally I could be wrong. What about the thermostat sticking open some and the radiator hasn't had time to cool the coolant down. John http://www.specialtauto.com/