Rear Defroster is used during winter months that melts ice or removes condensation from the rear window.
It is a system, to clear condensation and thaw frost from the front and rear windshield and side mirrors. For the primary defogger, heat is generally provided by the engine coolant thru a heater core. Fresh air is blown through the heater core then ducted to and distributed over the interior surface of the windshield by a blower
This air in many cases first cooled down and dehumidifier by passing through the vehicle's evaporator. This makes defogging easier for the dry warm air has a larger a capacity to absorb water from the glass. Secondary defoggers is composed of a series of parallel linear conductors in or the glass. When the power is applied these conductors heat up thawing ice and evaporator condensation from the glass .; These conductors may be composed of a silver ceramic printed and baked onto the surface of the glass.