Heater box removal on a 77

[Hunter]

Heater box removal on a 77 with AC

The heater box has been damaged on my 77. It has a crack on both pieces (halves). The blower motor half & the one closest to the exhaust manifold. What is the best way to pull these out to repair. I am going to try to fiberglass them if I can get them out.
Thanks in advance!!
Steve

 

[smurfvet]

This is for a heater box, not heater with A/C. They are both similar, but the A/C system adds a lot of fittings and piping that needs to be dealt with.

Around the outside of the heater box in the engine compartment are 5 nuts on studs. one is way in back on the heater motor scroll that you can only feel, at the far outside edge of the housing at 9 o'clock. I believe they are all 7/16" size. Usually, a nut driver is better than a deep well socket. Take these nuts and washers off, and remove the heater hoses. You might have to cut across the ends where the hose clamps are if they are stuck. Yanking on the hoses will only bend or break the tubing connections.

Disconnect the heater power lead, and you should be ready to go. The box may be stuck to the firewall, as they used "Permagum" rope sealant to seal the box watertight. A putty knife should be all you need to loosen the outer (engine compartment) half.

The inner half with the heater core is not as simple. Remove the right 1/3 of the dash (passenger side, and the center gauge cluster, including the radio. CAREFULLY pull the interior heater half into the passenger compartment. After you swing the box into the compartment, you can see the vacuul hoses on the damper actuators. Code these with tape, and remove. Then, the heater core and inner box half.

A couple of points- You cannot remove the heater core from the engine compartment even though you would swear you can. It HAS to come out from the inside, due to sheet metal baffles that re-direct the air around the heater core. While the box is out, check the foam seals on the diverting damper, seals around the core and the gasketing. They're probably shot. I believe some place on Long Island has repair kits for $25 or so.

My engine side box half was cracked due to some meathead trying (and failing) to remove the heater core without loosening up the inner half. He also broke off two studs that I replaced with bolts. The repairs with fiberglass was very easy. After painting, can't tell what was done.

Good luck.

 

[Hunter]

Thanks! This one does have Air, so I guess there will be more fittings???

 

[smurfvet]

Yeah. I think you would need to remove the half towards the engine and then jockey the A/C parts and hoses out of the way. On other GM cars, I believe that is how we got to the evaporator. Age is hell on your memory, though. Since you want to take the halves right out, move the aluminum coil and associated nonsense towards the engine and start working on the half under the fender next.

Your engine compartment box should split in half, I believe, right at the A/C evaporator. You can tell if that's it by the two regrigerant lines (one looks as large or as larger than a heater hose, one smaller, possibly aluminum). Don't fool with these! R-12 is 50 to 60 bucks a can, and you will probably need 3 or 4 to recharge the unit. Or else you are looking at a R-134a conversion- still not cheap if you do it right.

I think that there would be a similar, or slightly larger amount of the 7/16" nuts to remove from the covers with A/C, due to the larger size of the halves.

If you find someone with an assembly manual, that would show how the two pieces went together at the factory. There was one posted on a website, but I can't find it now. The assembly manual saved me a whole lot of frustration with the interior pieces and some of the "missing" things on my car. I think they're only 25 bucks or so. A REALLY GOOD investment!