A coolant is a fluid, that is used to reduce or regulate the temperature of a system, like an engine through a radiator, or for example, the passenger space by means of an air conditioner. In any of these systems, it is important that the continuous flow of coolant flow be monitored. This is achieved with flow switches mounted to and from the area that require cooling. This helps check that the input to the system has not reduced, and that the output from the system has the same rated % drop. A simple, cost effective reed switch based flow switch. Reed Switch based flow switches are available in different configurations, either normally open or normally closed, to close or open at a wide range of flows. This helps circuit designers be flexible with regards product selection. As long as the coolant is flowing at the required rate, the flow switch can either signal the controller. by chance, there is a block or if the coolant valve malfunctions, an indication is given on the instrument panel.