40 - iMac G5, 17-inch Troubleshooting Symptom Charts
4. If the dust has accumulated on the cooling fins then use compressed air from a can or
an air compressor to blow the dust from the heatsink as shown below.
5. Inspect the lower fan and use the compressed air to clean it out if needed.
6. Inspect the lower grill on the iMac front bezel and clean if needed.
7. Reassemble the computer and retest.
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 this speed once reached, the fans are most likely receiving
incorrect thermal input. In these cases you should use the following steps to resolve:
1. Reset the SMU (refer to “Resetting the SMU” mentioned earlier in this chapter) and
then test to see if the fans still exhibit the issue.
2. Boot from the iMac G5 Install DVD or another iMac G5 of the same type in FireWire
Target disc mode and see if the issue persists. If the fans run normally here, reinstall
the system software. Be sure to give the system enough time to recreate the issue
when booted to these other volumes.
3. Verify that the hard drive sensor cable is plugged in correctly. If necessary, replace the
hard drive sensor cable.
4. Replace the hard drive (the hard drive includes the sensor on the hard drive carrier.
5. Replace the main logic board.