Flex-A-Lite variable speed controllers attach on or near the electric fan, sensing coolant temperature via a radiator probe or temperature sending unit. They set fan speed from 60 to 100 percent, depending on the built-in thermostat’s setting. The thermostats have a range of 160 to 220 degrees F. The variable speed controllers allow greater control over engine temperature, which helps to reduce charging spikes and current load on the charging system. They will keep the fans running for 30 seconds after your vehicle is turned off.
This is hands down a far superior way to control ANY electric fan system. The fans come on slow, and only increase in speed if temps require it to… This equates to more consistent engine temps and less battery drain over the standard ON/OFF style fan controllers.