Fans are running at a constant high speed.
If the fans on the system are running at a constant high speed, or ramp very quickly to high speed and do not vary once this speed is reached, the fans are most likely receiving incorrect thermal input. Follow these steps:
1.Reset the SMC and then test to see if the fans still exhibit the issue.
2.Make sure the LCD temp sensor cable is fully inserted into the connector on the bottom left corner of the logic board.
3.Boot to the EF1 tests of the latest version of Apple Service Diagnostic, version 3S116 This will test the fans and thermal input of the sensors. If the tests fail, replace the component(s) indicated by the test.
