Heater Core

As best I can tell, according to Chilton's, it's not a simple job...

If you follow the heater hoses from the engine (on the passenger side) you'll see that they fit onto a pair of nipples on the firewall, one above the other. Those nipples are part of the heater core, which is contained in a plastic duct under the passenger dash. The nipples are near the inside edge of the heater core, so the heater core is mostly outboard (towards the fender) from them, but on the other side of the firewall, inside the car. The heater core is rectangular (perhaps about 12x18) and lies flat against the inside of the firewall, and the inside and outside air ducts sandwich the firewall between them, enclosing the heater core. I believe the inside duct has studs fixed on it that extend through the firewall and through the outside distribution duct, and those nuts sandwich the firewall and a pair of sealing gaskets between the two ducts..

On the firewall in the engine compartment you will see a molded plastic cover (distribution duct) held onto the firewall by nuts on studs... it is rectangular, with a round section on the extreme upper left as you look at the firewall from the engine compartment. There is a raised section of the duct cover that starts on the rectangle and ramps up/out towards the round section; that round section houses the heater blower motor (which sticks out another 3 or 4 inches); the blower motor may actually be beneath the top of the front fender and is bolted to the distribution duct.

The rectangualr portion of the cover/duct is roughly the size of the heater core behind it, but unfortunately the heater core doesn't fit through the hole in the firewall, it has to come out into the passenger footwell inside the car, which requires a bunch of other ductwork stuff be removed first.

Here are the instructions from a Chilton's shop manual for a NON-a/c car:

1. Disconnect the battery ground cable
2. Drain the cooling system and remove the water hoses from the heater nipples
3. Remove the air-distribution duct stud nuts on the firewall (about 8 nuts, I think) and move the cover outward off the studs (then you may want to plug the heater core nipples to avoid leaks when you remove the core)
4. Remove the right instrument panel pad, right side dash braces, center dash console duct, and the floor outlet duct.
5. Remove the radio and center dash console
6. Pull the distribution duct off the firewall from the inside... remove the resistor wires when clearance is sufficient (I think the resistor wire connects atop the distribution duct, 6 or

8 inches inboard of the heater core)

1. remove the heater core retaining springs, then remove the core
2. reverse the above to re-install

A while back in this thread, you mentioned that the temperature is low on the temp gauge. If you don't have heat in the engine, you won't get heat to the heater. Low engine temperature indicates that the thermostat is stuck open. It's a cheap and easy replacement - do this first before you start tearing apart the rest of the car. And get a friend who knows something about cars who can help you.

1976VetteGuy wrote:

I did replace the thermostat and it did make the temp go up...now I need to identify the heater hoses so I can se if they're hot...