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IF you are referring to the vacuum switch that resides in line on the heater hose.Most good parts houses have quality replacements in stock..IT controls opening and closing off the hot water that flows into heater box..and vacuum runs from there to beneath the ps dash behind glove box and opens closes the little flapper doors in the heat-A/C system..Gets its vacuum signal from the heater/A/C switch manifold under the console where the controls are..Before you change it out insure you have vacuum to the one vac line attached to the existing switch...
What are you calling a "vacuum switch"? The console HVAC control has vacuum connections, but also mechanical and electrical connections.
I am referring to the Heater/A/C control under the console. I have had to replace it twice no the replacements seem to not seal well. Looking for a good source. Thanks
There have been problems with the reproduction vacuum switch in the control head. I think Willcox Corvette is modifying the ones they sell to fix the issue. I suggest buying on from them.
Months ago I purchased a complete unit from Ecklers for just under 140.00.Works great.Wilcox offers modified-improved vacuum fitting that would mount on your existing console mounted assembly for under 30.00 Look at the blowup pic of the Ecklers unit and you'll see the component part offered by Wilcox.
Ecklers pn is 25-124795-1
There have been problems with the reproduction vacuum switch in the control head. I think Willcox Corvette is modifying the ones they sell to fix the issue. I suggest buying on from them.
Door that sends air to the vents will not open. Other doors work fine. When I put external vacuum on the center (tan) line the door opens and closes very very slowly. I now am thinking the problem is with the vacuum pot that controls the center door and not the switch. Wilcox told me what they do to the switch to make it more reliable. I did that and my switch seems to be working properly but the center door will not open. Probably just not enough engine vacuum however the other flaps, doors work fine. That center pot will be a challenge to service. I now have the entire duct system on my shop floor. Any ideas would be appreciated. Thanks
Door that sends air to the vents will not open. Other doors work fine. When I put external vacuum on the center (tan) line the door opens and closes very very slowly. I now am thinking the problem is with the vacuum pot that controls the center door and not the switch. Wilcox told me what they do to the switch to make it more reliable. I did that and my switch seems to be working properly but the center door will not open. Probably just not enough engine vacuum however the other flaps, doors work fine. That center pot will be a challenge to service. I now have the entire duct system on my shop floor. Any ideas would be appreciated. Thanks
Which dooris the issue?The one behind the glove box is affected by a cable as w ell as the vacuum line..The cable can be adjusted with a turnbuckle and is activated when the selection for mx cold is made on the console controls..Vacuum is simultaneously activated when blower is on high..the in line vacuum switch in the heater hose changes mode and shuts the hot water off to the heater itself..I haven't dug into the system as far as you have..but the above is my understanding of the sequence of events that happen when controls are activated.
Doc Rebuild is the guru on the old systems..and offers detailed schematics on most all the Astroventilation Corvette systems. http://www.docrebuild.com/dr-r-web/9222108.HTML
Last edited by jim in oregon; Jun 18, 2016 at 09:41 AM.
Don't know if this is related to your problem, but this is how I addressed my problem...
In 1977 I bought a new Corvette and within a couple of years, I noticed my temperature & heater control levers were no longer controlling their respective functions. On top of that I could now hear a small vacuum leak coming from that portion of the console. I removed the side panels and saw that the only thing holding the valve body together was a small plastic pin and it had broken and the valve body was no longer sealed and directing vacuum to the correct ports. Here you can see the small plastic pin in the center of the Heater Vacuum Control Switch... photo courtesy Paragon Corvette Reproductions
The cheap plastic clips failure was apparently a common problem even back then.
I happened to have a few small nylon screws ... (used to attach non-conductive surface to electronics bench), handy that were the exact size I needed. I ran a tap through the switch where the plastic pin had been and screwed the nylon screw in it's place after applying a thin smear of silicone grease on the valve body surfaces. The switch worked like a charm after that.
Don't know if this is related to you problem, but this is how I addressed my problem...
In 1977 I bought a new Corvette and within a couple of years, I noticed my temperature & heater control levers were no longer controlling their respective functions. On top of that I could now hear a small vacuum leak coming from that portion of the console. I removed the side panels and saw that the only thing holding the valve body together was a small plastic pin and it had broken and the valve body was no longer sealed and directing vacuum to the correct ports. Here you can see the small plastic pin in the center of the Heater Vacuum Control Switch... photo courtesy Paragon Corvette Reproductions
The cheap plastic clips failure was apparently a common problem even back then.
I happened to have a few small nylon screws ... (used to attach non-conductive surface to electronics bench), handy that were the exact size I needed. I ran a tap through the switch where the plastic pin had been and screwed the nylon screw in it's place after applying a thin smear of silicone grease on the valve body surfaces. The switch worked like a charm after that.
Good luck... GUSTO
I have done this type of repair many times and it never failed or leaked vacuums. The nylon screw looks good to me however I used a short fat sheetmet screw to replace the plastic rivet. When you tighten in the screw with the star spring washer make sure it's not too tight and the slide handle moves freely. I also lubed the rubber maze with a small wipe is vasoline. I got flamed hard when I presented this fix however it worked on 3 of my past cars and a couple others. The original pin or plastic rivit will break or get loose and the slide handle will move causing a hissing vacuums leak. A crew in it place is a permiante fix.
When I put an external vacuum source on that line only the door opens very very slowly. When I remove the vacuum the door closes very slowly Aldo. I am wondering if the vacuum pot is bad. When I plug the connector onto the control switch and put it in the vent position the door does not move at all. Seems like with an external source the door should open rather quickly. Help
Thanks
DO you have the 1978 ASSEMBLY INSTRUCTION MANUAL?AIM..
more that six pages showing what does what and how-why..
There's quite a bunch of components involved in proper operation of your HVAC system..
Many of the vac valves are not easily accessible sad to say..Jim
When I put an external vacuum source on that line only the door opens very very slowly. When I remove the vacuum the door closes very slowly Aldo. I am wondering if the vacuum pot is bad. When I plug the connector onto the control switch and put it in the vent position the door does not move at all. Seems like with an external source the door should open rather quickly. Help
Thanks
From what you describe, it's not the vacuum pod.. it's the part I show above.. When it breaks the plastic bends before the door moves.. I'd pull the center duct out and check it for sure before I go to the vacuum pod.. I have the vacuum pod to if needed.
I checked the part pictured and it was not broken. I now have the actuator out. (after an almost complete disassembly of the car) It will not hold vacuum. It does pull in slowly but will not hold position. At any rate I am going to put a new one in after all this work. Do you have a new one? I talked to you man at the number listed and he thought it might be a used one. I would reall like a new one although they have been known to fail right out of the box. Anyway thanks for your help. Let me know.
Bob
I checked the part pictured and it was not broken. I now have the actuator out. (after an almost complete disassembly of the car) It will not hold vacuum. It does pull in slowly but will not hold position. At any rate I am going to put a new one in after all this work. Do you have a new one? I talked to you man at the number listed and he thought it might be a used one. I would reall like a new one although they have been known to fail right out of the box. Anyway thanks for your help. Let me know.
Bob
Bob.. Email me at support@willcoxcorvette.com and let me check what I have. I may have new, but if not I can vacuum test a used pod and get it on the way to you quickly. I'm sorry for not seeing this sooner, I've been helping in our shop the last two days (it's killing me) putting a new engine in a 65.
