How to install a heater core

Here are some steps to replace the heater core in your 1979 Ford F250 Custom Pickup:

1. Disconnect the battery ground cable.
2. Remove the air cleaner.
3. Drain the engine coolant below the level of the heater core.
4. Remove the heater hoses from the heater core.
5. Remove the screw fastening the A/C hose support bracket to the firewall.
6. Remove the insulating tape covering the valve.
7. Remove the two screws holding the plate over the opening that the A/C hoses exit the evaporator housing.
8. Remove the plate and the seal.
9. Remove the glove box liner.
10. Separate the A/C duct from the register in the instrument panel and free the clip holding it to the plenum.
11. Remove the duct from under the dash.
12. Remove the vacuum hose from the vacuum motor on the right-hand side of the airbox.
13. Remove the rear housing cover from the evaporator housing. The cover is retained by 4 nuts and one bolt.
14. Disconnect the fresh air tube from the rear cover.
15. After removing, reinstall one nut to secure the evaporator housing to the firewall.
16. Gently remove the capillary tube from the evaporator core.
17. Disconnect wires from icing sensor and remove sensor plate.
18. Remove plenum by extracting two screws above transmission tunnel that hold plenum to dash.
19. Remove screws securing evaporator, pull it from case and secure it above case.
20. Remove heater core and heater air control door (retained by spring clip).
21. Remove arm supporting air control door and retainer securing pivot arm.
22. Remove blower motor and transfer blower wheel to new motor.

After removing old heater core, you can install new one by reversing these steps.

You can also check out these videos for a visual guide:

• 1979-1986 Ford F150 F250 Heater Core Replace How-To
• 73-79 Ford Truck Heater box removal (The right way!)

Please remember to take necessary precautions while working on your vehicle, including wearing appropriate safety gear and ensuring your work area is well-ventilated.

1979 Ford Truck Parts Catalog may also be of interest to you.