The temp lever in my 82 broke off. I removed the control unit from the console and found the remains of the lower lever not being able to move the cable. The frozen cable probably is the reason for the lever breaking in the first place when the previous owner tried to force it in a certain position. When I turn the adjustment screw in the cable, it moves, but only towards the lever.

The other side oft the cable is connected to the water shut off valve behind the glove box. Is this a known area for the cable to lock in or rust tight? What is needed to free the cable so I can replace the lever and get the temp control back working?

 

The cable runs to the temp control lever and we typically don't see issues with rust in this area. The hot water shut off valve is hit by this level when you move the temp from hot to cold.

New cables are available but you can probably soak the old one and get it working again. With the cable off, check the free movement of the lever too...

https://willcoxcorvette.com/corvette...itioning-77-82

 

Checked on the cable today and found the lever behind the glove box frozen. Broke it loose, cleaned it with brake cleaner and lubricated it. Soaked the cable with WD40 and now it moves freely. I also replaced the lever in the control unit in the center console. So far, so good.

Now, the prong in the shut off valve travels only, say, 1/4 of an inch. However, when I move the lever in the control unit from cold to hot, the lever behind the glove box travels about an inch. In other words, the valve is fully open when the control lever is at the beginning of the white field.

Is there a way to adjust this somehow? I read about a cap on the lever behind the glove box somewhere?

 

The "button" on the hot water shut-off switch (the one in those pictures) is only supposed depressed by the lever when the temperature control is all the way to the left (cold). It looks like it is being operated correctly.

It is a simple on-off vacuum switch. When pressed you should get vacuum at the hot water shut-off valve. It is in the engine compartment on the passenger side near the A/C accumulator.

The temperature lever has a lot more travel because it is operating a damper that diverts a varying amount of system air through the heater core. Unfortunately such is either poorly effective by design or perhaps seals become less effective as they age but unless that shut-off valve closes you will ROAST in the cabin in warm weather without A/C and your A/C will never get truly cold regardless of setting. From what I understand this was actually an improvement over previous versions which often finds owners installing a manual ball valve in the water line to the heater core.

If you have a hand vacuum pump or other vacuum source now is a good time to test the HVAC system. The main vacuum connection to the system is in the engine compartment. It's on the driver side fairly close to the distributor. You'll see a "T" with two small and one tiny vacuum hose attached. The tiny hose operates the HVAC.

With the system in the "OFF" position it should go into significant vacuum with a single pump and stay that way for a LONG time--think overnight and/or days. You can then move the function selector and apply vacuum at each setting. You should hear things moving a bit and once you get a fair amount of vacuum it should hold indefinitely in every setting. Don't forget to test with the temperature lever all the way "cold".

A leaking selector switch is fairly common. It's easy to disassemble. Clean it and apply some heavy silicon grease and it will probably work like new and better than the cheap replacements.

 

Are you saying the "general" on/off regarding hot water is being controlled by depressing the button at the shut-off valve while the actual temperature is being controlled by the switch/unit behind the face in the center console?

And yes, I have never owned a C3 that doesn´t roast your feet, but I blamed that rather on the transmission than the heater layout.

 

Yes, that is EXACTLY what I'm saying. Such may not apply for all C3s but certainly from '78 on that combination of hot water shut-off switch and shut-off valve will absolutely stop all flow of hot water to the heater core. Your driver foot will no longer roast as long as the temperature lever is all the way to cold.

The problem with my '79 was a late production design change that found the same hot water shut-off switch used in an '80+ with let's say a semi-flexible make-it-longer-but-still-"feeling" extension condom applied to that short little button. Not surprisingly the extension lost connection to the shaft after repeated use of off-center pressure.

 

Thx. I will check if the temperature adjustment works and might need to get back on this.