I suspected a problem with my thermovalve and contacted Monaco Tech support and they told me to do 2 things.
plugged both lines and the fan ran wide open.
put a union in between both hoses and the fan ran at an idle
These 2 tests show that the switch control is good and that the thermo valve is bad.
I bought a thermo valve from White House Products in UK, cost ~$265 including shipping and Exchange rate.
My part # is 553/1/09857/210 THERMO VALVE took about a week to get after placing order.
2002 Monaco Windsor 38 PKD
2005 Jeep Grand Cherokee w/5.7 Hemi