Heater alternatley blows hot and cold air while idling

cmjohnson24, the heater core for the heating-A/C system is located in the HVAC housing, behind the instrument panel. It is a heat exchanger made of rows of tubes with fins. The heater core is positioned within the HVAC housing so that only the selected amount of air entering the HVAC housing passes through the heater core before it is distributed through the heating-A/C system ducts and outlets. The heater core tubes are attached to the side of the heater core and are secured to the HVAC housing by a removable flange. The heater core can be serviced by removing the HVAC housing.

The removal of the heater core and maintenance of it is very involved.

NOTE: The HVAC housing must be removed from the vehicle and disassembled for service of the heater core, A/C evaporator, mode-air and blend-air doors.

1. Recover the refrigerant from the refrigerant system (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - STANDARD PROCEDURE - REFRIGERANT SYSTEM RECOVERY).

2. Drain the engine cooling system (Refer to 7 - COOLING - STANDARD PROCEDURE - COOLING SYSTEM DRAIN).

3. Disconnect and isolate the negative battery cable.

4. Remove the instrument panel from the passenger compartment (Refer to 23 - BODY/INSTRUMENT PANEL ASSEMBLY - REMOVAL).

5. Remove the two bolts (1) that secure the HVAC housing (2) to the passenger compartment side of the dash panel (3).

6. Disconnect the A/C liquid line and the A/C accumulator from the A/C evaporator and install plugs into or caps over the fittings and evaporator tubes (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING/LINE-A/C LIQUID - REMOVAL) and (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING/ACCUMULATOR-A/C - REMOVAL).

7. Disconnect the heater hoses from the heater core tubes and install plugs into or caps over the heater core tubes.

8. Remove the three nuts (1) that secure the HVAC housing (2) and the fresh air inlet screen (3) to the engine compartment side of the dash panel (4).

9. Pull the HVAC housing assembly rearward so that the mounting studs and condensate drain tube clear the dash panel and remove the HVAC housing from the passenger compartment.

10. If required, remove the fresh air inlet screen from the dash panel.