Is the fan switch the coolant temp sensor? The one that controls the temp guage. I think mine is malfunctioning. the fan will not turn. After i put in the hypertech chip it stayed below 180 with the fan running. But now the fan will not turn on unless by itself. if i ground the fan it works so that is why im guessing the fan switch.

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85 Z/28
Mods: Flowmaster's,Cam,Hypertech Chip

 

Have you moved your battery lately? The fan relay swith runns right by it and if you move the battery it might disconnect it. This happened to me so its worth checking. Good luck.