Repair Heater Core

heater core
The heater core is a miniature radiator that sits in the dashboard area. When the heater is turned on, it opens the heater valve which lets hot coolant into the heater core, which then warms the air coming into the vehicle's interior.
A heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air.
A finned unit located in the passenger compartment and through which coolant from the engine flows to heat the unit. A fan blows air over the unit to heat the passenger compartment

repair
Make good (such damage) by fixing or repairing it
restore by replacing a part or putting together what is torn or broken; "She repaired her TV set"; "Repair my shoes please"
the act of putting something in working order again
Put right (a damaged relationship or unwelcome situation)
a formal way of referring to the condition of something; "the building was in good repair"
Fix or mend (a thing suffering from damage or a fault)