[77newell]

The cooling water temp has a lower "limit" determined by the thermostat in the engine. My 93 coach has a direct drive fan and the engine runs at the setting of the 180 degree thermostat in the engine regardless of outdoor temperature unless headed up a steep hill on a hot day, then it rises a bit.

So, if your engine is running cooler than the coolant thermostat in the engine you probably have a failed thermostat.