1999 kenworth t2000 with detroit 60- fan won't shut off.

I have same issue I tried all of this and all your procedures are pritty much rite I would say its ac as well probly the plug at ECM or in the wireing harness from there to AC pressure sensor. I have the cummins INSITE and with that you can see what component is making your fan stay on for example mine say air conditioning switch wich is the pressure sensor in this case I know this because I used INSITE and disabled Air conditions pressure sensor in 2 diffrent place on parameters. And fan worked fine. But of course truck had to go to work so I couldn't finish fixing. But I will tell you what INSITE told me to do it says to do a resistance check from pin on ac plug to pressure sensor plug. If both wires have no resistance the wires are good otherwise of course there is a bad spot somewhere in that harness. If it's all good and you have checked or changed pressure switch I'd assume it's in ECM. Because it sounds like you allready changed every thing else. Any way get back to me.

 

Take jumper wires hook to batterie and put one to each terminal on air soleinoid if fan changes it is wireing before the fan soleinoid. Also make sure air is going to fan soleinoid. If it is wires before fan silanoid the way to check is unplug wireing harness for ECM find pin for fan and check the resistance with a multimeter on those wires should be none 0000.000 if it has resistance that wire is the problem witch you can splice rite after ECM plug I'd give a lil extra. And put new wire up to soleinoid. Sorry I don't have wireing diagrams fan solenoid should be side of heater box. I'm not sure what ECM pin it is sorry I got no diagram ither.

 

Any luck let me know how it turns out

 

On passenger side behind the step you got your air tanks and on the back side of them tanks there's some sensors , one with two wires , mine was green after I cut and sliced it back together my fan worked normal, was having the same problem