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68 vette everything on the vacuum system is new... all hoses ,accuator,etc...got car running a month ago...worked through the electrical problems,,,now working on vacuum system...I took hose off brake booster and bypassed tank..nope...tried override valves..nope..electric switch behind tach is clicking ..switched hoses on it in case I did that backwards..nope...headlight canisters work and wiper door canister works ...but not by vacuum system..bypassed headlight switch also..nope...could it be the vacuum switch in the nose and by the blower motor is bad? I have tried some things as you can tell...I think there is a thread on how all this works...any suggestions...THANKS..Malcolm
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
you need to get yourself a cheap vacuum pump so you can check for leaks. I got a cheap a/c pump and put a valve in line and pull 15 inches of vacuum then shut it off. Then operate you switches and see what is leaking. Its hard to hear anything with the motor running, easy when its quiet.
Go To the Willcox tech section and search there. Lots of good info. Upate this thread as you progress
FYI the headlight switch controls the vacuum for the headlights and the wiper switch controls the relays for the wiper door. You have 2 different sub-systems for each of the systems. One vacuum source tells the actuators to open or close, the other system does the openning or closing
Do an advanced search here and you will find years worth of issues and how they go tsolved
so, you have put a hose on up and down on both headlights and they move correctly? there is a long vacuum hose that goes thru rad support from intake to the t fitting before actuators. has a bug nest o other blockage in it. you need to feel vacuum on the big and little hose in front of the radiator. big hose gets plugged up a lot. the 2 vacuum actuators also have blockages in them.
ok both holes you are looking at are fresh air intakes. the smiley one provides atmospheric pressure to blow the lights up when the relay puts vacuum on the other side of the diaphragm. vacuum doesn't really do the moving. it just removes the pressure so the atmospheric pressure on the other side blows the light upwards. well, the piece of scotchbrite called an air filter over those dissolved about 20 years ag. now that hole attracts wasps. makes a nice nest. plugs up the air path and the lights open s-l-o-w-l-y and close at normal speed. stick a 3/16th drill bit up there and spin it around and it will get it out.
Last edited by derekderek; Feb 23, 2022 at 08:42 PM.
vacuum system doesn't work on anything
