This control is designed specifically to greatly reduce the shock to the electrical system as the 70 amp relay kicks in. In order to make a smoother start up, we separated the two legs of the fan so they start at different temperatures, thus the surge is much lower or about 25-30 amps at a time. The setting for the first fan is set to your preference. The second leg is turned on just a few degrees higher then the first so the cooling ability is not affected. It also shuts down sooner so that you run on far less amperage as quickly as the engine temperature levels off. Both legs have separate circuit breakers and relays. If one leg should fail, the second leg can still operate independently to keep your systems under control as well as possible. A 70 amp surge is certainly difficult on even a high amperage alternator.
It has an adjustable operating range of approximately 140 degrees to 230 degrees. The sensor is simply tightened under an intake or water pump bolt.. It is equipped with an A/C Request system to turn the cooling fan on whenever the A/C Compressor engages (this feature does not have to be used). This system is a simple install and dial in one temperature. No Electronic "programing" involved
Since you are using an electric cooling fan, you'll need an alternator that can put out 65 amps AT AN IDLE. This is different from the "typical 100 amp alternator" you hear so much reference to. That "100 amp alternator" is at highway speeds and has nothing to do with what it is capable of at low speeds like a traffic light when that fan is working the hardest. You need to ask both numbers when you are buying one.
This is important and will make a difference as to how well the fan works when you need it most. To properly control that alternator, we need to know how many amps is draws. There are the typical models that have been around for quite a while that draw around 30 amps.
This system has two relays and two resettable circuit breakers. If one leg should fail, the second leg can still operate independently to help keep your systems under control as well as possible.