How to replace heater control box and cables 1967-72 Chevy GMC C20 Suburban truck

When your heater control arm breaks in your 1967-72 Chevy GMC Suburban truck due to stuck control cables or binding lever arms, it's time to replace everything.
If your level control arms haven't broke yet, but are getting harder to operate, you may avoid this hassle repair by removing all 3 of your cables and lubricating them so they glide easily. This is the number one cause of the lever arms breaking... stuck cables that are rusty or binding. They're not hard to replace with new ones altogether, but you may not want the expense of buying new ones if you can salvage the old ones.
Next, you could try to repair the arms or rebuild the control box unit, but replacing the entire thing is cheaper and easier if you use a few of my tips in the video along the way.
You could also reuse your old cables if you can get them lubricated and sliding and gliding easily again, but if there's any resistance, just replace them with new.
There's one trick that I show near the end of the video about how to reinstall the locking push-on retainer on the hidden heater door. It's incredibly difficult to access, and if you're not careful you could break the heater door arm, resulting in a serious tear-down and repair.
I also show my trick for removing those pesky push-on retainers (some call them locking star washers, or speed washers). But be careful removing them from the brittle pot metal lever arms!
Lastly, PLEASE follow my advice about labeling your cables and you remove them, especially if you're not reinstalling them the same day. I made the stupid mistake of thinking I would remember which cable went where... WRONG! Just label them, or take a picture.