Another vote for "got to have a fan shroud!"
The fan clutch should be spinning the fan some at idle. It should continue to spin as you bring up the engine speed. Once the air temp coming across the fan clutch gets to a certain point, the coil on the front of the clutch moves and allows the oil inside the clutch to further lock up the clutch.
My experience with fan clutches has been all over the place over the past few years.
I bought a good thermostatic fan clutch for my truck and it works ok, but it seems to always be "on" and spinning the fan hard all the time, but gives up at too low rpm.
I then tried the HD version and it sounds like a Cessna on takeoff but does keep my truck cool all summer, but takes quite a bit of power to run as its "on" all the time. ( It finally unloads after about 3000rpm.)
So now I have a third one. An old half worn out clutch off a Suburban that I run in the winter, then when the heat hits, I put on the HD one and run it 'till fall comes.
Sometimes its a balancing act between good cooling and not sucking 20 horsepower off the engine trying to keep the heat down.