I had a simialr problem on my 01 Imperial several years back. I did the troubleshooting to identify the exact casue. Of course when I took it to Wildwood, Fl for repair they didn't take my word for the casue and did 10 hours of troubleshooting to come up with the same cause as I did and I paid t=for that ten hours.
Anyway, read this article on hyraulic fan systems.
https://www.centralstatesbus.com/wp-content/uploads/2003_BBAA/a3pdfs/a3hydfan.pdf
The fan speed is controlled by a fan control valve. A wax valve on the radiator controls the fan control valve. When the arva is cold and temp is below 185 degrees, the wx valve blocks most hyradualic fluid from going though the wax valve and thus to the fan control valve. Therefore, the radiator fan spins at a low speed. When the temperature of the engine and coolant increase the wax valve allows more fluid to pass to the fan control valve and thus the speed of the fan increases. Since your fan is spinning fast, the wax valve could be faulty and is much cheaper to replace (~$140) than the fan control valve assembly (~$1500 plus hours of labor).
A simply test to determine if the wax valve is faulty is to remove the two hoses connected to teh wax valve and use the proper fitter to cap the two lines. This will result in no fluid being returned to the fan control valve assembly and therefore should result in the fan spinning very slow. If the fan speed is still high then the fan control valve assembly is faulty but if the fan speed is low then teh wax valve is bad and needs to be replaced.
In 2016, Alliance (now lazy Days in Wildwood, FL) charged me $3811 to replace the fan control valve assemblya and various hydraulic hoses. I also replaced the wax valve myself that i purchased off ebay for about $100. I keep the wax valve as it was replaced only because of the other work, it never failed. I also kept the fan control valve assembly to have rebuilt if needed.
If your fan control valve is bad, contact Precision Fluid Power at 1-800-728-5168 to see if they can rebuild your unit. If the wax valve is bad contact: http://www.nwrvsupply.com/product/553109857190.html to see if they have one.
Sorry the part number mean nothing to me as I have no cross reference.
Good luck
Murray Walker 01 HR Imperial