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1982 Corvette. AC not cold inside car. Had it recharged but I don't seem to have any vacuum to the valve located in the heater hose at the evaporator and the water is hot both sides of valve. Everything seems to be connected and no damaged lines that I can tell. The controls for heat and AC seem to be working the doors to change it from floor to dash etc. Need to know what part to check on this.
1982 Corvette. AC not cold inside car. Had it recharged but I don't seem to have any vacuum to the valve located in the heater hose at the evaporator and the water is hot both sides of valve. Everything seems to be connected and no damaged lines that I can tell. The controls for heat and AC seem to be working the doors to change it from floor to dash etc. Need to know what part to check on this.
The hot water valve is supposed to close when you select Max AC. Many do not over time. Sound like yours is due to loss of vacuum to that valve. Likely the controller. Even if it does close the heater core can still get hot over time from the return hose.
Lots of guys put in shutoff valves in at least the supply hose and also the return hose if they truly want to stop the heater core from heating up.
The hot water shutoff valve is behind the glove box. The box liner is easy to remove and you'll see the valve and cables on top of the plenum.
#2 is incorrect with regards to '78+ when saying that the valve is operated by setting the system to MAX A/C
A lever attached to the cable presses the switch plunger when you put the temperature selector all the way to "COLD". Such is the ONLY way to operate the hot water shutoff valve. If the temperature cable is misadjusted it may not move far enough left to operate the switch.
The hot water cutoff switch is very easy to test.* One of the hoses on the switch goes direct to manifold vacuum; the other direct to the valve. The port which leads to the valve gets vacuum when the plunger is pressed; otherwise it is open to air.
*A hand vacuum pump makes it easier and since it has three connections but two hoses it can be hooked up improperly.
The hot water shutoff valve is behind the glove box. The box liner is easy to remove and you'll see the valve and cables on top of the plenum.
#2 is incorrect with regards to '78+ when saying that the valve is operated by setting the system to MAX A/C
A lever attached to the cable presses the switch plunger when you put the temperature selector all the way to "COLD". Such is the ONLY way to operate the hot water shutoff valve. If the temperature cable is misadjusted it may not move far enough left to operate the switch.
The hot water cutoff switch is very easy to test.* One of the hoses on the switch goes direct to manifold vacuum; the other direct to the valve. The port which leads to the valve gets vacuum when the plunger is pressed; otherwise it is open to air.
*A hand vacuum pump makes it easier and since it has three connections but two hoses it can be hooked up improperly.
Thanks for the info. I did check the cable and it seemed to be working the switch but I did adjust it and now have vacuum to the valve. I figure if it quits now it probably is the controller working intermittently.
Appreciate your help.
Hello, I found this thread because I too am having trouble with my 1981 Corvette not having vacuum to the hot water valve. I think I have found the cable adjustment under the center console passenger side. I'll try and post a pick. My question is which way do I turn the adjustment?
towards the left- drivers side or the right?
Hello, I found this thread because I too am having trouble with my 1981 Corvette not having vacuum to the hot water valve. I think I have found the cable adjustment under the center console passenger side. I'll try and post a pick. My question is which way do I turn the adjustment?
towards the left- drivers side or the right?
you need to see how it hits the shut off valve. You can see it after removing glove box liner. The cold setting lever needs to stop about 1/4 inch short of hitting the bezel so it pushed the plunger on the hot water shut off switch.. https://www.corvetteforum.com/forums...79-w-ac-3.html
Willcox corvette has a diagram but site down at moment..
I will also add, that the vacuum switch for a Late 1979-1981 is visually a different switch.
I like the later switch much better because the travel required to activate the vacuum switch is much shorter.
And you can actually carefully open the switch for cleaning and to re-lubricate the inner spool using Vacuum Grease.
The short vacuum line on the right "I" attached to this switch is showing vacuum in.
The center port (when button is pushed in) is the vacuum signal to the hot water shutoff valve in heater hose.
The left off center port is the exhaust port.
Screwing the two halves of then adjustment turnbuckle together shortens the cable sheath, which moves the heat lever end of travel towards the left (cold) side. Unscrewing them changes travel towards warm. The idea is to hit the plunger with the lever when the lever is near the end of its left travel to shut off the water flow.
I found the whole mess to be a PIA, so I replaced the vacuum switch with an electric one:
Thank you for your input. When I pulled the glovebox, I could see that when I moved the temp control it did not move the cable at all to shut the valve.
When I saw this, I notice that the cable had come detached from the HVAC control at the point where a plastic tab slides into the HVAC control and serves as an anchor point to allow the cable to move within the plastic housing. When I held the cable at that point and moved the trmp control it would shut the valve.
As I see it, I will have to replace the HVAC control as I am sour glue will not hold and may damage both parts. See pictures.
That stinks. Hopefully you can find a decent used one that’s not too pricey.
fwiw, I’m guessing someone in the past got aggressive with the lever trying to shut off the heat and broke the attachment point. Exactly the problem I was trying to avoid with my “upgrade”.
I looks to me the plastic slot where the tab of the cable slides in has broken off.
See if it didn't fall under the carpet or surrounding are, then try a good 2 part epoxy made for plastic.
Broken slot may look something like this.
Yea, that someone was me a few years back. I have owned the car for 22 years, and while adjusting the cable to shut off the valve behind the glove box today idiot me was not paying attention and pulled the metal ball off the cable where it attaches the temp controller. I have ordered a new cable and HVAC controller from Ecklers this evening, expensive for what they are but if I could even fix what is broken, I would be afraid it would not hold, and I would have to take everything apart again.
I'll keep everyone up to date.
Air conditioning
