Originally Posted by RWW6542
Yeah to both ?
It is a NO. There is no relay in the hydraulic fan system. The PCM controls directly the hydraulic control solenoid which is mounted on the hydraulic fan motor. (the relay under the headlight is only for the electrical cooling fan setup until 2003)
Regarding the speeding up of the fan with the AC on, i never heard my fan speeding up when the AC is switched on, even on the hot days we have overhere. But the PCM gets the pressure signal of the AC system and it can speed up the fan, depending on this pressure signal.
But your problem should not be related to the cooling fan, since it runs warmer on the highway, when the fan is not supposed to be working, and cool when at idle.
Oveheating this engine is a NO-NO, it will easily warp heads when overheated.
There is a good change that a head gasket is leaking after the overheat. It would be wise to do a pressure test on the cooling system, to see if there is an internal leak. If there is an internal leak, you mostly see that the cooling system overflow reservoir stays full, but that the level in the radiator is low.
Also when the radiator is full and there is a headgasket leak, you can see air bubbles in the overflow reservoir. You also need to check the engine oil, to see if no coolant is mixed in the oil. (which creates a white foamy substance.)