1977 climate control vacuum diagram

[vmrod]

With the past experiences of Bobchad and 77-4 speed, I was able to open up my dashboard, and check my vacuum lines.

As most of us C3 owners know, things tend to heat up in the driver's compartment. Sometimes the fix can be something so simple, as to re-attaching a vacuum line, or plugging up one that is no longer in use. (typically the heater hose bypass valve actuator)

I created a vacuum diagram for the climate control system, and it also shows a single control cable to a 'flapper' vent. The file is zipped and is in .PDF format.

Bobchad has several nice pictures on his homepage depicting these connections, and a check-list is posted there as well. (authored by 77-4 speed). With all of this information, it should be easy to get your vette, back to normal enviromental temperatures. (The worst part is the dashboard removal)

In the past, I posted a cruise control diagram as well, which can reference this diagram for the vacuum input.

 

[Bob Chadwick]

Vic has provided me with all of these diagrams and pictures and I will be incorporating them into the page. Probably this weekend before I get around to it. I can post the url for the web page as a technical reference if someone will tell me where and how. I thought the knowledgbase would be the appropriate area but I'm not so sure after looking there.

Bob

 

[vmrod]

A most excellent idea!!
I will be quite satisfied if we can help out some fellow enthuisiasts!

 

[handyforgod]

I need the heater/ac vacuum diagrams.

A most excellent idea!!
I will be quite satisfied if we can help out some fellow enthuisiasts!

If you read this, please respond with a copy of the 1977 heater/ac diagrams I hear everyone talking about. my email is csheran@verizon.net.

Thanks in advance.

Carl in Riverview

 

[Bob Chadwick]

Vacuum Diagram

 

[handyforgod]

1977 vacuum diagram

Vacuum Diagram

Thanks a bunch Bob, very good, descriptive schematic. I appreciate you!

Carl in Riverview.

 

[kazebiker]

I'm new here, just registered last night. I bought my wife a black 77 L48 for Christmas and am slowly getting the problems ironed out. As with most classics I've bought this one has had the wiring and vacuum components "modified" (read hacked). when I got it home I replaced the rag joint and freed up the distributor mech advance among other things. It is her daily driver and she loves it. I took the dash apart yesterday and started unfixing all the jacked up stuff that the previous owners did, there is quite a bit that needs attention. Thanks to this website I am having much success. Just wanted to say thanks to everyone.

 

[73shark]

Welcome to CAC. Sharks are a lot of fun.

 

[handyforgod]

Need some more help on AC controls.

Using Bob's diagram, we were able to trace out the vacuum lines as shown, butr we are still having problems

The problem we are having is getting vacuum to the Green/Black lines going to the Exterior Vent door and the interior vent door. What control settings allow for vacuum to activate the closure of the outside door and the opening of the inside door? Nothing we do seems to work. I also note that the rubberized seal on the outside door flap is very hard and drags across the fan mount base when it does attempt to close, something we can't seem to do consistently. Can anyone tell me the control settings for these two valves to function? Is the hot to cold mechanic valve in play here or just the varied vacuum switch in the control body. We ordered and installed a new one to no avail since his old one was broken. Bob C mentioned that the only time the footwell opens is on max air. This is when the outside vent should close since they are supposed to be on the same vacuum circuit. Is there any history on the clear rubber connecting plug to the switch going bad, since it is a 1977 vintage piece of rubber and perhaps there is a vacuum leack caused by that.

I told the owner that the stiff edge seal may be part of the problem but there is something more causing a lack of vacuum.ad Maybe I should tell him to install ALL new vacuum lines to his control circuts. Just trying to help the guy out since he is old like me but does not know how to talk on the internet.

sincerely,

Carl in Riverview

 

[Bob Chadwick]

Carl,

I didn't pick up on the vacuum issue when you PM'ed me. You may want to pickup a MityVac Vacuum Gauge and start to check to see if your lines are holding vacuum.

Bob

 

[tonyponykay]

I dont want to hijack thread, just wondering:

i took my console apart, and found a black and yellow vacum line attached to nothing and nowhere for it to attach. Its not long enough even to attach to the temp control mechanism. My main problem is that everything, a/c and vent and heater all blow through the bottom of the dash.. nothing comes through the vent except a tiny breeze that isnt even really a breeze, might be my imagination.

mine is 1980, restoring it, wondering if anybody in this thread might know anything? don't know if i should just start my own thread or ? don't know cause i'm kind of new to this site and sites like this site.. I'm very happy to find this site though

thanks
tony

 

[mysticstriper]

I'm with you TonyPony, don't mean to break in but I have the same problem you do. The diagram was helpful, but as I'm going along I'm finding more vacuum lines that are not connected. My A/C is blowing cold-on my left leg. There is no breeze coming through the vents at all. I'm about to pull the entire dash out and start the repairs but it would be helpful to find a complete vacuum line diagram somehow. PLEASE if anyone knows some tricks or has the diagrams, I could really use the help.
Thank y'all!
BTW, I'm new on the forum, have a gorgeous 1980 L82 with a 383 cid, 1999 Trans Am with the LS1 and a 93 Mustang GT with a 450 hp 306 cid. They are all fun, but NOTHING feels like my vette-I can't find the words for it, it's a luxurious corner carver even though my Mustang blows it away performance wise I don't care. The Vette just "feels" right to me.

 

[My77Vette]

Access to valve

To gain access to the plunger switch that is actuated by the heater control cable from the console, do I only need to remove the dash to the right side of the console or do I need to remove center console too? My heat is constantly blowing and I do plan on installing cutoff valves in the dupply and return line, but I would also like to get the vacuum lines figured out and the switch replaced too. Thanks for the diagram Bob! Very helpful.

 

[Mr. Sharky]

I just acquired a 1980 that seems to be the Vette from Hell. Regarding the A/C issues, I too have air only coming from my feet area. I did notice that cold air is blowing out at the base of the windshield near the passenger side fender. I have vacuum coming in to the car. But no matter what I do, I still have air only blowing to my feet. Did any one of you fix your issues?

 

[bill81vette]

I just acquired a 1980 that seems to be the Vette from Hell. Regarding the A/C issues, I too have air only coming from my feet area. I did notice that cold air is blowing out at the base of the windshield near the passenger side fender. I have vacuum coming in to the car. But no matter what I do, I still have air only blowing to my feet. Did any one of you fix your issues?

Have you checked to see if any of your vacuum line are in tact or have been unhooked or been attacked by Mickey Mouse???
from your question I would check all of those first...there are some behind the glove box,as well.
Do you have an assembly Instruction Manual or a factory service manual?????

 

[Mr. Sharky]

Have you checked to see if any of your vacuum line are in tact or have been unhooked or been attacked by Mickey Mouse???
from your question I would check all of those first...there are some behind the glove box,as well.
Do you have an assembly Instruction Manual or a factory service manual?????

I have to look for my manuals. But I did look at all the vacuum lines and I did not see any thing that was not connected. I am going to have to go back in there and test each line for vacuum.

 

[bill81vette]

Best thing to do, is find your manual and check each line.
if that doesn't work you'll have to check your selector to see if its working properly,other wise you'll have to get into the doors to see why they are not working.

 

[73shark]

Since the condition described is the default position for the divertor door, I suspect either no vacuum or a bad vacuum diaphragm.