headlight goes down slow

by Keith
(Port St Lucie , Florida)

C3 Corvette Headlight Vacuum Diagram

C3 Corvette Headlight Vacuum Diagram

When I put the headlights on both go up. When I turn the headlights on the right headlight goes down but the left headlight will only go down if I rev the engine up to create more vacuum

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Jan 21, 2016
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Vacuum Leak
by: Chris

Well the good news is its either a vacuum leak or maybe another vacuum leak. Seriously though vacuum leaks are such an issue for C3 Vettes. Its a little smoke and mirrors to troubleshoot but not to bad once you get the hang of it while using the proper tools. Make sure you reference the diagram above for our discussion.

Check all hoses for condition and cracking with engine running at idle.

Check for proper engine vacuum at point "2" and "K" and compare each point. They should be the same. If not you have a leak in the hose leading to the tank.

Next Check Vaccum at Actuators "E" in operation and compare to tank vacuum once again these should be the same. If not check Relays "D" and hoses.

The goal is to isolate and test for leaks.

Next Vacuum check with a 2 in 1 Brake Bleeder & Vacuum Pump Test Tuner Tool
by applying vacuum to the return side of the Corvette Headlight Actuator, With Boot & Seal
"E" after disconnecting all hoses. Do this for both sides. Repeat for the Vacuum Actuator Relay
. A properly functioning component will draw and hold a vacuum.

Notes:
Small leaks add up!
Make sure you order the correct parts as the years and locations matter. Good luck and let us know if we can help you any more!

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