Apple iMac (17-inch Mid 2006) - Manual (Page 141)

iMac (17-inch (Mid 2006/Late 2006 CD) Troubleshooting — Symptom Charts 141
Fan Sound
Fans running at full speed after the computer turns on
The customer may have entered a diagnostic mode that causes the fans to run at full speed.*
Restarting the system will not restore normal fan operation. To solve the problem, the user or
technician should do the following:
Shut down the system.
Disconnect the power cord and wait 15 seconds.
Reconnect the power cord and wait 5 seconds.
Power on the system.
*Note: Customers reporting this symptom should be told to press the power button AFTER the
power cord has been fully inserted. Inserting the power cord while pressing the power button
will cause the fans to run at full speed.
Loud fan noise coming from inside the computer
The iMac has a trio of fans that circulate air throughout the system. It also includes temperature
sensors, and advanced thermal software that spins the fans fast or slow as needed. As the system
usage increases, the fans will adjust their speed using advanced thermal software to meet the
cooling needs of the system.
Under normal conditions, rotating fans will make a slight hum that varies in relationship with
their rotational speed and the amount of air that they are moving. In addition, the normal
functioning of the hard drive and optical drive will generate additional whirring and scratching
sounds that may be audible. All of these sounds are normal and do not indicate a failure with
your computer.
To begin troubleshooting a possible fan issue, we need to qualify the sound that you’re
experiencing.
Does the sound occur only under specific light/heavy usage conditions?
Yes: CPU intensive applications such as iTunes, Garage Band, DVD Player, etc., or two or more
applications open at once will cause the fans to run at an increased rate making them more
noticeable. If the sound only occurs when one or more of these applications is running, this
is normal.
No: If the sound isn’t affected by CPU intensive application it may be due to other factors. Go
on to the next step.
Is the sound always present, or does the sound vary?
The sound is always present: The normal functioning of the hard drive and optical drive will
generate additional whirring and scratching noises that may be audible. Check whether this
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