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The cleaning fan on 9000 and 9010 series consist of a series of caged fans on the same shaft. Although it looks difficult it isn't too bad. The first step is to remove the drive belt and the left side drive pulleys. Next you will need to unbolt the plastic shrouds from the floor plate. (The below link will take you to the diagram showing the hardware mounting locations)
Once the shroud hardware has been removed you can then drop the lower floor #16 down this then allows you access to the fan assemblies from below.
Next loosen the clamps holding the fan assemblies to the shaft itself.
Once the fan clamps are loose slide them off so that they sit on the hex shaft.
Remove the bearings from both sides and slide the hex shaft out the left side of the machine. The fan assemblies may need to be tapped gently to break them free of the hex shaft.
You can use a light multipurpose oil on the hex shaft when reassembling the new fans on the shaft. This will make the fans easier to put on.
Make sure you install both bearings and lock collars before you tighten the fan shaft clamps in place. Use care to make sure all fan assemblies are centered in the shroud.
If you need any further detail please let me know.