Directions to Remove the Heater Core in a 1995 GMC

The heater core in your air-conditioned 1995 GMC C1500 truck is a fairly simple heat exchanger device that exchanges the heat from engine coolant with the cold of outside air. This process heats the passenger compartment of your truck. If the heater core develops a leak and the leak goes undetected or unrepaired for any length of time, you run the risk of overheating the engine and causing serious engine damage. On this vehicle, the heater core is located in the air box behind the glove box in the dashboard.

Instructions

1

Place the drain pan under the radiator drain valve and open the valve by turning it counterclockwise. Remove the radiator cap by pushing down and turning it counterclockwise.

2

Loosen the clamps on the heater hoses where they meet the bulkhead between passenger and engine compartments by turning them counterclockwise. Grasp the hose end and twist back and forth while pulling the hose off the heater core nipple. Do this for both hoses.

3

Remove the glove compartment. This may require a Phillips screwdriver, a Torx (star bit) screwdriver or a small socket and ratchet. Label any electrical connections and vacuum lines going to the air box and disconnect them. Gently twist and pull vacuum fittings. Depress electrical fitting latches and pull apart.

4

Remove the air duct running along the floor. Again, this may require using a Phillips screwdriver, a Torx bit or a small socket. Screws, bolts or nuts will be turned counterclockwise.

5

Open the passenger door and remove the hinge pillar trim panels. These are normally secured with two Phillips screws which will need to be turned counterclockwise. On some trucks, the ECM module will need to be removed from the mounting plate and set aside. Don't disconnect it.

6

Locate and remove the large round blower motor cover and then remove the blower motor. Turn the nuts or bolts counterclockwise with the appropriate tool.

7

Remove the bolts that fasten the heater case to the bulkhead by turning them counterclockwise with a ratchet and socket and remove the heater case from the truck.

8

Remove the seven screws that close the heater case by turning them counterclockwise with the Phillips screwdriver. Remove the brackets and fasteners that secure the heater core in the heater box and remove the heater core.

9

Replace and re-secure the heater core in the box. Re-assemble the heater box and tighten the screws.

10

Mount the heater box to the bulkhead and tighten the screws and nuts as follows: lower screws to 17 inch-pounds, upper screw to 97 inch-pounds and the nuts to 25 inch-pounds by turning them clockwise with the appropriate tools.

11

Attach the heater hoses to the heater core nipples, slide the clamps to a half-inch from the hose ends and tighten them until they won't move when force is exerted on them by turning them clockwise with the straight screwdriver.

12

Install the blower motor and cover and tighten the screws until they don't turn when moderate force is applied. If removed, re-mount the ECM module. Install the trim panels, lower air duct and glove box in the reverse fashion of removal. Connect any electrical leads and vacuum lines removed previously. Close the radiator drain by turning it clockwise by hand.

13

Fill the radiator until the coolant level reaches to just below the fill opening neck. Start the truck and allow to come to operating temperature while checking for leaks. Top off the level as needed. Make sure the overflow bottle is at the recommended level and fill as needed. Check for leaks.