Keeping you Ready for the Road Ahead™, the AirSource 5/8” Manual Heater Shut-Off Valve connects to a 5/8” heater hose, effectively stopping coolant flow from going to your heater core. This action is needed when the heater is not being used during hot months or you are experiencing an emergency leak in the HVAC system. Opening the shut off valve during cold winter months ensures your cabin is properly heated, no matter how harsh the environment may be outside your truck. FleetPride is your First Click in Heavy Duty®.