Oldssupreme

Hi! I hope you’re all well. It’s been a while. Can anyone help as to what I am missing from the circled piece on top of my AC heater box for my 1972 Cutlass supreme? I have the warm/cool control attached with the cable in front of it over to the pivoting S shaped grooved piece circled in yellow. However, I am not seeing anything attached to the top control of the user interface where it says heat, defrost, vent, normal, max. Does that control have a cable that attaches to the blue circled piece included in my photograph? Just want to make sure before I put this back up on the firewall. Also, can anyone Help with what size and type nuts fasten the box onto the firewall on the engine side? I cannot find the nuts so I need to get a new set. I’m assuming they are some sort of “cymbal” type fastener. Thank you so much!

joe_padavano

The A/C system used vacuum to operate diaphram actuators on the HVAC box. The only cable is to operate the heater blend door, which is what you show in your photo. Heater-only cars used cables for all the functions, but A/C cars did not.

Oldssupreme

Hi Joe! Good to hear from you. Thank you for your quick response. And to be sure, am I good installing the box as it is and adding the ductwork after I secure it to the firewall? Also do you know the correct type and size of nut to use to secure this to the firewall? Thank you!

joe_padavano

It's actually been a while since I've had one out on the 70-72 cars. Assuming the dash pad is in place, You'll want to have the center duct and defroster hoses in place first. The correct nuts are actually stamped sheet metal nuts. GM part number is 9419845. AMK sells them under P/N B-12959. Most restorers sell them also, especially since they are used on Corvettes.

Oldssupreme

Thanks Joe! Once I see the photo of the stamped nuts I found them right away- safely stored on my firewall. That’s what happens when I don’t get to work on the car very often.