Apple Hardware Test may incorrectly report the error "2FAN/4/8 : Rear Fan 0" on Power Mac G5 (Late 2004) computers if the air deflector is not installed. (Remember that the air deflector should always be installed when the computer is running.)
It is possible that the error does not indicate an actual fan failure. To verify whether it is a genuine failure, follow the steps below to reset the SMU, make sure that the air deflector is properly installed, and run the test again:
- Shut down the computer.
- Disconnect the power cord from the wall socket (or from the power strip) and wait at least 15 seconds.
- While you're waiting at least 15 seconds, open the door on the Power Mac G5 and make sure the plastic air deflector is firmly in place.
- Reconnect the power cord and start up the computer.
- Run the Apple Hardware Test again. If the error persists, have the computer serviced.