Finding a good fan controller for PowerPC Macs has proven to be a difficult task. After extensive searching the best option appears to be G4FanControl which is listed below.
 

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A MacRumors user (ForI) noticed that some temperature values were present within the Apple Fan extension. Follow these steps to modify these values:
 
  1. The AppleFan.kext is located in System/Library/Extensions/AppleFan.kext
  2. Right click on this file and select ‘Get Info’
  3. Under ‘Sharing and Permissions’ change the privilege for ‘everyone’ to ‘Read & Write’.
  4. Right click on the file and select ‘Show Package Contents’, then open the ‘Contents’ folder.
  5. Open the Info.plist file and replace the relevant values with the ones below:

            <integer>13300</integer>
            <key>fan-polling-period</key>
            <integer>8</integer>
            <key>fan-slowdown-delay</key>
            <integer>16</integer>
            <key>fan-speed-table</key>
            <array>
              <integer>13800</integer>
              <integer>14200</integer>
              <integer>14600</integer>
              <integer>15000</integer>
              <integer>15500</integer>
              <integer>16000</integer>
              <integer>15500</integer>
              <integer>16768</integer>
              <integer>17200</integer>
              <integer>17800</integer>
              <integer>18176</integer>
              <integer>18700</integer>
              <integer>18950</integer>
              <integer>19100</integer>
              <integer>19150</integer>
              <integer>19200</integer>
            </array>
            <key>fan-speedup-delay</key>
            <integer>8</integer>
    
  6. Save and close the file.
  7. Open the 'Terminal' app and run the following command:
    sudo chown -R root:wheel /System/Library/Extensions/AppleFan.kext 
    This prevents a dialogue appearing at the next boot stating that the extension was installed improperly by resetting the file's ownership permissions back to defaults.
If you find any better solutions please get in touch.
 
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