Removing the Old Core

• 1). Drain and recover the refrigerant from the cooling system. The system must be cool and the engine off to avoid injury.
  
  
• 2). Remove the quarter trim panel on the right hand side. Detach the upper air duct on the auxiliary housing and remove the auxiliary line bracket.
  
  
• 3). Clamp off and then disconnect the heater hoses. Disconnect the drain hose, blower motor and the electrical connectors for the blower motor resistor electrical actuator.
  
  
• 4). Remove the auxiliary climate control housing and the access cover to the evaporator/heater core. You can now remove the heater core.
  
  

Installing the New Core

• 1). Install the replacement heater core into the Navigator and replace the access cover and climate control housing. Reconnect all hoses and electrical connectors, using new O-ring seals where they are needed.
  
  
• 2). Clean and lubricate the coolant hoses if necessary, using plain water. Lubricate the refrigerant system with clean PAG oil.
  
  
• 3). Connect the auxiliary line bracket and the upper air duct. Reconnect the quarter trim panel.
  
  
• 4). Refill the engine coolant level. Test the refrigerant system for leaks with a refrigerant leak detector. Evacuate the system of air and charge it with an R-134a Service Center.