Your fan limit switch will have a small white button on the lower left corner. That button tells the switch whether to operate manually (run the fan all the time) or automatically (run the fan only during heating cycles). If the button is pressed in, the switch is set to Manual and is forcing the fan to run continuously. (3) - The JET Fan Switch Harness is only required if main cooling fan control is desired. (4) – This model is equipped with a secondary-cooling fan that is controlled by the ECM/PCM. 1984 Corvette – The main cooling fan is controlled by a brass cooling fan switch identical to the JET 60603.
The Cooling outlet supplies power at 78° and cuts off at 70° and works great for all types of fans including exhaust, circulation, window, attic, and ceiling fans. The Heating outlet supplies power at 35° and cuts off at 45° and is great for automating heaters to keep room temperatures above freezing.