GM 21999768 Blade Assembly, Engine Coolant Fan

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If the radiator is overheating and the Radiator fan is not coming on when the radiator temperature rises to an excessive level, check the fan relays in the under hood fuse/relay box. If the relays are okay, check all wiring and connections to the fan motor. If no obvious problems are found, the problem could be the Engine Coolant Temperature (ECT) sensor or the Powertrain Control Module(PCM). Have the Radiator fan system and circuit diagnosed by a dealer service department or repair shop with the proper diagnostic equipment. To remove and install the fan assembly, start by disconnecting the cable from the negative battery terminal. Then, raise the vehicle and support it securely on jackstands. Remove the splash shield and drain the cooling system. Detach the upper radiator hose from the radiator and position it aside. Remove the air filter housing and intake duct/resonator. On ZL1 models, unclip the air deflector from the top of the fan shroud. Disconnect and plug the coolant overflow hose from the radiator filler neck. On V6 and non-supercharged VB engines, disconnect the upper radiator hose clamps and remove the hose. On supercharged VB engines, disconnect the charge air cooler hoses from the fan shroud. Slightly reposition the transmission cooler lines without disconnecting them, if equipped. Disconnect the fan harness electrical connector and detach the wire harness clips from the fan shroud. Remove the fan shroud-to-radiator mounting bolts and lift the fan/shroud assembly from the vehicle without damaging the radiator cooling fins. To detach the fan blade from the motor, remove the nut from the motor shaft and remove the fan blade from the motor. To detach the motor from the shroud, remove the retaining bolts and disconnect the electrical connector. Installation is the reverse of removal. When reinstalling the fan assembly, make sure the rubber air shields around the shroud are still in place-without them, the cooling system may not work efficiently. Reconnect the battery and refill the cooling system. Start the engine and allow it to reach normal operating temperature, then check for leaks and proper operation.

If the motor is okay, the problem may lie with one of the fan relays. There are three cooling fan relays that can be checked and replaced if necessary.