Cat 15 engine fan won’t turn off parts replaced

probably a broken wire in the harness .... my guess is ground wire for the high pressure swtich. A shop with Cat ET should be able to tell you what is kicking on your fan.

 

Most times I run into that is high pressure switch connector. Sounds like you already changed the costly stuff.

 

Could be the jumper harness to the high pressure a/c switch is not making a good connection. Had this same problem before and a new harness fixed it.

 

Could be your lossing air if the fan not getting air it will run all the time i had the same problem the airline that goes to the fan put your hand an follows it to find air leaks it had to find cause the engine has to be running.