The heater core in your Dodge Ram is like a small radiator. There are a series of tubes through it, carrying hot water, and a blower attached to the unit then sends air over the heated tubes through the cab of the truck. A heater core that is leaking will leave the floor inside of the truck wet. If there is a clog in the heater core, it will block the liquid from flowing properly and you will get no heat in the cab. In either case, you will need to replace the heater core. The project is not difficult, but it will take some time. Plan on setting aside an entire afternoon so you aren't trying to rush the job.
Disconnect the negative cable from the battery using a wrench to loosen the terminal nut. Open the valve on the bottom of the radiator with a wrench and drain the coolant into the drain pan. Place the drain pan out of the reach of children and household pets.
Discharge the air conditioning system using an approved fluorocarbon recovery kit. Disconnect the refrigerant line from the evaporator inlet tube using a wrench. Remove the accumulator from the Dodge by disconnecting the lines with a wrench.
Disconnect the heater hoses connecting to the heater core using a screwdriver to loosen the clamps. These hoses are close together and connect to the firewall.
Move to the inside of the Dodge Ram and remove the instrument panel using a screwdriver to loosen and remove the screws. Remove the powertrain control module from the dash using a screwdriver to remove the screws, but do not disconnect the wiring.
Move to the engine compartment and remove the four mounting studs that secure the heater/AC mounting brace to the firewall using a wrench. Move back to the passenger compartment and remove the nuts securing the mounting brace to the studs of the heater/AC unit using the wrench.
Pull the heater/AC unit housing toward the rear far enough that the mounting studs and drain tube clear the holes in the dash panel. Remove the unit housing from the Dodge and remove the heater core from the housing.
Install the new heater core into the heater/AC housing. Place the housing through the dash and onto the mounting studs. Attach the nuts to the mounting bracket and tighten them with a wrench. Move to the engine compartment and attach the four mounting studs using a wrench.
Attach the powertrain control module to the dash and tighten it with a screwdriver. Install the instrument panel and tighten the mounting screws with the screwdriver.
Move back to the engine compartment and connect the heater hoses to the heater core. Tighten the clamps with a screwdriver. Install the accumulator and connect the lines using a wrench. Connect the refrigerant line and tighten it with a wrench. Recharge the AC system using an approved AC charge kit.
Refill the radiator and reservoir with engine coolant. Connect the negative battery cable and tighten the nut with a wrench. Start the engine and bring it to operating temperature. Check for leaks inside the cab and in the engine compartment.
Properly recycle any leftover chemicals. Do not place them in the trash.
