I can not speak highly enough about the Hollister Road guys or their products. About four years ago or thereabouts I spoke to them about building an enhanced version of their Auto Cool 85 which was a 85 AMP fan controller for a Lincoln Mk VIII fan.
I wanted to run an electric water pump along with the fan and I didn't want to load my electrical system with both the water pump and the fan's current draws. They built the controller for me. Today it is available on their site for anyone to buy, click here =>
Auto Cool 85 RT. I originally paid several times the price it is available for today but mine was the very first and essentially a custom build.
What the controller does is seamlessly ramp fan and water pump speeds up and down to maintain a target engine coolant temp you specify. When you get to highway speeds and the electric fan is not needed the controller shuts off the fan. When you park the car the controller will run both the electric water pump and the fan for a minute or so after key off to help cool down the engine and prevent hotspots.
When you use the controller you no longer use a thermostat because it creates a closed loop system tracking coolant temp at the engine coolant outlet on its way back to the radiator and seamlessly raises or lowers both fan and water pump speeds to maintain that target temp you set. It's like a hound dog tracking a rabbit, it never stops and it is dead on target.
Very nice product, extraordinary people.
Ed