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Old 01-26-2004, 11:51 AM
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Vacuum questions

First let me apologize if this is in the wrong area
On the 76 Vette (and others) the headlights run off vacuum to open and close mine didnt work. I did some trouble shooting and found the vacuum lines were not connected to the headlight switch. After I hooked em up they work great when I turn them off (they go down) when I turn em on I still have to pull them up manually. I checked all my valves with a vacuum pump and they all check fine. The only thing I didnt check is my headlight switch because I couldent get to it, but when i turn the headlights on i can hear vacuum escaping from the switch which i believe is suposed to happen heres why:

TROUBLESHOOTING: When closed (knob pushed in) attach the vacuum pump to port 2 and block port 3. Vacuum pressure should be maintained. When open (knob pulled out), port 3 will not hold vacuum. Attach the vacuum pump to port 2. vacuum pressure should hold.

port 3 comes directly from the manifold I believe thats why I hear the hissing

Under the front bumper there is a vacuum resivour about 2 ft long and maybe 8 inches in dia, does this need to be completely full of vacuum (that sounds stupid) for the headlights to go up..There spring assisted closed so I assume it wouldent take much vacuum to close but much more to open them against the spring

Does anyone have a clue about vacuum headlights I think im on the right path just need to wait longer and have more vacuum in the resivour

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Old 01-26-2004, 09:34 PM
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Ecklers sells a good 10 page troubleshooting guide for the Vette vacuum head lite system. It costs around $10 and is very helpful. It sounds like you have your vacuum lines mixed up. Your lite system is spring loaded to raise the lites up to the on position in case of a system failure. You should Not hear any vacuum noise at the switch. You can bypass the switch to "on" by connecting the two lines at the switch. You should have vacuum readings equal to manifold vacuum almost immediately at the reservoir, if you don't, you've'e got a leak. I downloaded a hose diagram into my gallery for you.
Good Luck.
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