Kenworth T300 engine fan issues

I have a 2006 KW T-300 with a Cummins ISC at 320 hp. It has been running hot lately, just over 200 degrees and the fan is not coming on like it used to. It still comes on but intermittently. Does any one know where the fan control sensor, relay, and/or module is located? All I can find it the temp gauge sensor on the manifold below the coolant tank on the driver side firewall. The software has the fan coming on at 185 degrees or with the air conditioning but not with the engine brake since it has an Allison auto with the transmission retarder and not a true engine brake. Computer does not show a demand for the fan even when coolant temp reads over 185 so I am assuming it is either a bad sensor, relay, or controller. If I put air directly to the fan it will come on, have not tried putting a trigger signal to the air valve for the fan yet because I don't know if it triggers at +5 or +12 VDC, or being Kenworth if it uses a negative trigger.

Sad part, I wouldn't even know this was an issue if the truck didn't blow a hydraulic line yesterday and I swapped it with our driver, he never noticed it was getting hot but I did within 5 minutes of driving it back to our yard.

Suggestions? Thanks in advance.