engine fan stays on

hello drivers im new to this forum and very new to the O/O seen.. I just purchased a 1998 international with a M11 cummins. it has an issue right out of the gate that I cant figure out.. the engine fan does not shut off at all.. ive tried jumping the ac switch at the compressor and no luck.. when the engine is off and the key is on the fan releases but as soon as the truck is running it locks up and never stops.. there is no override switch on the dash.. its gutless as it is just being a little motor but this fan is making it a real dog and my fuel milage is in the low 5s any help would be greatly appreciated.. thanks jeff

 

okay what switch the ac switch or the air switch?? I guess I could just get both and see what works.. im just hopeing its not the clutch.

 

10-4 heavyd I will go out now and do just that..

 

okay jumped the switch let it run for 20 mins.. checked the switch with a test light and it has a closed circuit... I checked the wires as well as I could without ripping the harness from the truck and didn't see anything bad... I ran direct hot and ground to the fan air control switch and the fan stoped!!! could the temp sensor be bad telling the ecm its hot??? also the ecm was replaced before I bought the truck and I just got it 2 weeks ago don't know how long this has been going on but its done it since the test drive.. could the ecm need programming??? im at a loss shes a good horse I want to get her right!!

 

not sure I understand the valve plumbed open or closed.. on this one the top air line runs to the fan