Fan clutch stuck? The tool I used to fix.

[DVT873]

Sometimes a two wire solenoid will short to the case. These are usually bolted to something metal. The short will cause problems if the solenoid is ground controlled thru the one of the two wires. A while back had a run of bad ones new, right out of the box bought from OE in this case Navistar. To get going ended up strap tying them to the wiring harness bundle. Then they worked fine.