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Fan not spinning up after replacement

I was working on replacing the loud and old fan on my iMac G4. I cut off the connector of the old fan, and determined the polarity as follows:

Cable color iMac → corresponding cable on replacement fan (Arctic F9):

Black → striped black cable

Red → middle cable

Yellow → outer black cable (not striped)

When connecting the old fan like this to a USB adapter, it spins up. Installed in the iMac, the new fan doesn‘t spin up and isn‘t „detected“ by the OS (10.4.11). How can i go about testing the polarity of my cables is correct? I do have a multimeter available, i just don‘t know what to measure.

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1 Answer

The fan has a tachometer within it so the logic board can monitor the fan. The fan you got likely doesn’t offer that ability

Reference this guide iMac G4 17 800 MHz EMC 1936 Fan Replacement

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2 Comments:

Thank you! Is there any way to find a fan that would offer this functionality, or add it using an adapter?

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@janhiebert23214 - Sorry I don’t know where you can get the proper fan unit. The best you can do is look for a junk system which has a different problem to get the needed fan unit.

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Jan Hiebert will be eternally grateful.
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