How to Put in a 2002 Nissan Altima Heater Core

The heater core is located in the dash to provide heat to the vehicle's interior.

The heater core in a 2002 Nissan Altima provides heat for the interior of the vehicle to warm it and to melt ice from the windshield. It functions as a small radiator. The engine circulates heated coolant through the heater core and cool air from the vehicle's interior is passed over the cooling fins in close proximity to the heater core. This causes the air to be heated and the coolant to be cooled. The average life span of a brass heater core is 5 years or 50,000 miles. Before assuming that a heater core is plugged, check the other parts of the climate control system.
Difficulty: Moderately Challenging
Instructions
Things You'll Need
Set of metric sockets and ratchet handle
Set of metric combination wrenches
Screwdriver
Pliers
Hose removal tool
Drain pan
Hose clamp removal tool
1

Disconnect the negative battery terminal from the battery. Discharge refrigerant from the system. The law says that you must evacuate the refrigerant and recover it into an EPA approved machine to limit the amount of refrigerant that enters the atmosphere. Many service facilities will do this for you for a fee. Open the drain petcock on the radiator and drain the coolant into a pan.
2

Loosen the heater hose clamps from the hoses connecting to the heater core pipes. Disconnect the refrigerant lines from the evaporator, which is located close to the heater core. Remove the instrument panel by removing all of the securing bolts and clips. Remove the glove compartment of the vehicle, along with the electronic control module located behind the glovebox. Remove the heater blower fan and motor assembly.
3

Disconnect the heater mode door motor. This is the door that controls which vents that the air comes out of. Disconnect the air mix door motor connectors, and remove the heater and cooling unit from the vehicle and place it on a bench. Remove the heater core pipe support screws and the heater core cover screws.
4

Guide the heater core outside of the heating and cooling unit by opening the section up and pulling it out. Place the new heater core inside of the heating and cooling unit, and reassemble the unit. Put the heating unit braces back on the unit, and reinstall it in the vehicle.
5

Continue following these steps in reverse order to complete the installation. When the complete system is reassembled, close the radiator drain petcock and refill the cooling system. When the radiator is full, start the engine and allow it to heat up to open the thermostat.
6

Put the heater control to the highest heat setting to allow coolant to fill the heater core and hoses. Run the engine, topping off with coolant, until the heater blows hot air and all air bubbles have stopped coming out of the coolant in the radiator. Recharge the air conditioning system to the manufacturer's specifications.

Tips & Warnings

Spray some silicone lubricant on the heater core pipes to make it easier to remove the hoses in the future.

Do not remove the radiator cap or open the cooling system when the engine is hot.