928 Fan Controller
 

I think the Fan Controller Unit on my 928 GTS is out. Can anyone suggest where I might find a used one?

Are you referring to the secondary fan controller mounted under the hood at the front of the car?
You may have the same problem with buying a used fan controller as you have with the one currently mounted in your car.
There are several folks that can rebuild them. You can ask several specific 928 parts suppliers for recommendations.

Did I just answer a "bot" post?

928 International has them in stock

You can try checking Porsche-specific forums, eBay, or salvage yards that deal in European or high-end cars. Also look at 928 International or 928sRUs, they often carry used parts. Just be sure to match the part number before buying.