Another electrical issue 06 vovlo vnl 670

My friend I have a Volvo + Cummins 06
And my Fan Clutch is staying On all the time.

We already replaced the solenoid and fix an open circuit connection on the computer

The fan by itself looks good mechanically.

What it might be? What to look for?
Driving me crazy. Truck is Old but in great shape.

Ivan

 

You need to check high side a/c switch and/or the wiring. With Insite you can turn off a/c switch operation so if fan stays off you know there is a problem with high side. I have 4 cm870 ECM's that I have collected over the years that work perfectly except for engine fan operation. The fan is stuck on with all 4.

 

How can I do that?
Am I going to have to end up at the dealership or is there any other option?