If you own a '66-67 Chevelle with factory A/C, it's no secret that the original heater and A/C control levers are a problem you will have to address sooner or later. We're betting on sooner. The control arms are constructed from pot metal and are notoriously weak; they've been known to give up at the slightest hint of a heavy hand. Of course, none of us would ever be guilty of such an infraction ... it's always the fault of a previous owner, right?
Although we'll be working on a set of '67 controls here, they are very similar to the '66's with only slight production variances. The procedure for replacing the levers in either year, however, is virtually the same. Like most setups we've seen, our middle arms were the ones "out of control." This is probably due to the fact that they mechanically control, through sliders and cables, the mechanical movement of internal "doors" in the A/C system to accomplish their jobs.
Of course, the problem of a poor design and even poorer materials is compounded by the fact that the cables they actuate are usually corroded and difficult to move as well. So, in order to maintain the function of the controls after you've restored them, we also recommend removing the original cables, lubricating, and "working" them until they slide freely. Or, if they're too damaged, you should consider replacing the control cables at the same time.
Before beginning, you may want to hit the books. That means sticking your nose in the appropriate service and assembly manuals. Doing so will give you an idea of how the components work together, as well as diagrams of how all the parts are assembled.
We ordered our new control levers from National Parts Depot (NPD), and just to be safe, we popped for some new cables as well. The new levers are fabricated from steel and will function well for many years. The replacement cables, however, differ slightly in appearance but are the correct length and function just like you'd expect new ones to. And while we had NPD's catalog open, we also spec'd a new control panel lens, so everything would look as good as it functioned. With our parts in hand, we were ready to begin the process. Our first step was to disconnect the battery to prevent any possible shorts or other electrical dangers while we're working.