im pretty sure its the temp ie fan switch that turnes them off as just driving allong the road they should not even come on.. defeats the object of the fan switch all together.. they should come on at a set temp cool the car and go off.. but mine when i plug the switch in the rad come on once in traffic and never go off even on the move.. once caar stops i turn off the engine and the fans stay on for about 30 seconds and go off.. if i re start the engine the fans are not on again until car reaches temp and the same thing happens.. where as now just using the in dash switch i normally switch fans on as soon as i stop in traffic or lights and switch off as soon as moving.. which is a pain in the arse but i can live with it but if i forget some time it gonna fook it right up.. all parts i can think of are brand new also.. but if their was a problem with the actuall cooling im sure the engine would have showed some sign of it by now.. i have run out of ideas..