hvac vacuum
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Instructor
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hvac vacuum
ok this is another post the lil selector switch was replaced for the heating and a/c. all vacuuum lines are hooked up and in place. when a/c switched to max all vents open. when switched to a/c normal the def closes leaving the main door open. when switch through heat vent and def nothing opens or moves. what opens the floor and cowl vent and what should open the def vent. totally lost on this one too. HOW DOES IT ALL WORK HELP!!!
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thanks but as i said all are hooked up right and in the right places i replaced the selector switch a/c side of the switch will function all the right diaphrams. when moved into the economy side heat/def/vent no vent diaphrams will open. is it a bum switch i replaced the lil rubber maze part. or is there 2 differnt one for a car with a/c and one without and maybe got sold the wrong one?
Burning Brakes
Joined: Mar 2010
Posts: 943
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From: Valdosta Georgia
Oh, my mistake! It's possible that you may have gotten the non-a/c switch. I had a similar problem, but mine turned out that the vacuum feed under the hood had gotten disconnected, but if you are getting proper operation on the ac side, i don't think that is your problem. Maybe a collapsed hose under the dash is the culprit? Just stabbing in the dark here...
Team Owner
Joined: Jan 2006
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From: Crossville TN
The Chevrolet Chassis Service Manual for your year will have all the diagrams and servo logic in it under the A/C section. I know of no other document that has all the info on vacuum, electrical and mechanical aspects of the A/C system. Along with the A.I.M., that is an indispensible document for a C3 owner.
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Thread Starter
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well i tested all the hoses with a pump and all open and close with the pump so its gotta be on the switch side. was there 2 different switches one for a a/c car and one not. will poke and prod some more today need to get a few this done before i can replace the interior and this is one. thanks for th einput 
Team Owner
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From: Southbound
Cruise-In II Veteran
Might be. AC was optional 77-79. There may be AC and non-AC 77-79 switches.
AC became standard with the 1980 models. There would be no non-AC switch after 1979.
Good advice from 7T1Vette; the AIM and chassis service manual show the vac hose routing, correct color codes, and the various door functions from the switch settings.
AC became standard with the 1980 models. There would be no non-AC switch after 1979.
Good advice from 7T1Vette; the AIM and chassis service manual show the vac hose routing, correct color codes, and the various door functions from the switch settings.
Last edited by Easy Mike; Jul 7, 2010 at 12:35 PM.
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well i might have to grab one. but assuming with common sense. That the MAX A/C opens all vents def and heater door which that does that. NORM A/C should just be the heater door for dash vents which it does open that. DEF should be the def diaphram. HEAT should be on the floor all closed possible the heater door for dash vents. and VENT should open the cowl and pass kick panel vent.
It's when you move from the a/c side to the economy side the heat vent def. it does nadda zip squat. thats why i was wondering if in 77 there was 2 diff switches as i knew a/c in 77 was a option.
As i mentioned earlier all lines are connected properly as per a diagram i managed to dig up. all diaphrams will function and hold open with a hand pump. so i am believing i pretty much sourced it to that switch. i bought the switch from corvette world but they only show one and didn't ask if there was a none a/c and a a/c switch.
It's when you move from the a/c side to the economy side the heat vent def. it does nadda zip squat. thats why i was wondering if in 77 there was 2 diff switches as i knew a/c in 77 was a option.
As i mentioned earlier all lines are connected properly as per a diagram i managed to dig up. all diaphrams will function and hold open with a hand pump. so i am believing i pretty much sourced it to that switch. i bought the switch from corvette world but they only show one and didn't ask if there was a none a/c and a a/c switch.
Burning Brakes
Joined: Aug 2000
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From: Morgantown,WV USA
ok this is another post the lil selector switch was replaced for the heating and a/c. all vacuuum lines are hooked up and in place. when a/c switched to max all vents open. when switched to a/c normal the def closes leaving the main door open. when switch through heat vent and def nothing opens or moves. what opens the floor and cowl vent and what should open the def vent. totally lost on this one too. HOW DOES IT ALL WORK HELP!!!
Good luck!
Dan
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mines a 77 and has the same switch as you with the lil circle maze rubber ring. i contacted corvette world and they basiclly said 1 of 4 sold don't work lol and i took that lil part a part and tried bending the circle spring tabs to where they would press a lil tighter with no luck. the nut and bolt sounds pretty good didnt think of that one will try and see what happens thanks
Team Owner
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From: Crossville TN
Hmmm.... A 25% failure rate--and YOU get to be Mr. Quality Control. What a deal these vendors have! Buy junk, sell junk, let owner discover junk, then claim "it was good when we sold it to you". But, they may have a good 'replacement program'. You know,
"If the one we sold you fails, send it back and we'll give you another one...just like it!!!
"If the one we sold you fails, send it back and we'll give you another one...just like it!!!
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lol yup called them and told them what the issue was they said sure bring it back we will replace it just wish the vette drove i would place it in while there 1 outta 4 be my luck their whole shelf wouldnt work 
better replace 15 bucks for a piece of rubber and plastic shoulda kept the oem one.
