[jhv48]

Disconnect the fan and take for a drive.

The temp should hover around 180-190 without the fan in fairly brisk driving at 50 degrees.

The temp should climb as you sit idling without the fan. Don't let it get too high.

If the above temps are realized, the problem is in the fan switch. It should not be coming on till at least 200 degrees. Replace the switch or install an adjustable switch that will turn the fan on automatically when a specific temp is attained (say 200 degrees).