Headlight Vacuum
Thread Starter
Burning Brakes
Joined: Nov 2005
Posts: 840
Likes: 19
From: Oshawa
Headlight Vacuum
I've just reinstalled my headlight system, my problem is that the lights go up slowly, when I testedthe vacuum it was only approx 14 lbs. If I increase the RPM the lights do go up quicker. Is 14lbs too low? Is there anything I can do to increasethe vacuum? Any help would be appreciated, the car is a 1971.
Thanks,
Rick
Thanks,
Rick
Burning Brakes
Joined: Jul 2006
Posts: 1,047
Likes: 12
From: SoCal
There are lots of potential factors at work here. 14" sounds about right (I think others here have said 10" is "enough" to operate headlights and wiper door, 10"-20" is normal range with about 15" at warm idle).
Have you checked for vacuum leaks - cracked hoses, leaking actuators (including the wiper door actuator)?
What about the engine - is it stock? If not, lots of other things to look at (where you are pulling vacuum from, what manifold, what cam, etc.).
If you test vacuum at one of the headlight actuators and at the vacuum source hose (on the carb), how do the two readings compare?
And what RPM are you idling at?
Have you checked for vacuum leaks - cracked hoses, leaking actuators (including the wiper door actuator)?
What about the engine - is it stock? If not, lots of other things to look at (where you are pulling vacuum from, what manifold, what cam, etc.).
If you test vacuum at one of the headlight actuators and at the vacuum source hose (on the carb), how do the two readings compare?
And what RPM are you idling at?
Last edited by VCuomo; Aug 22, 2006 at 08:32 PM.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by harrin
I've just reinstalled my headlight system, my problem is that the lights go up slowly, when I testedthe vacuum it was only approx 14 lbs. If I increase the RPM the lights do go up quicker. Is 14lbs too low? Is there anything I can do to increasethe vacuum? Any help would be appreciated, the car is a 1971.
Thanks,
Rick
Thanks,
Rick
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
www.corvette-101.com
This website has some pretty good instructions for checking the headlight vacuum system. Look for the link at the left hand side of the page, Vacuum Trouble.
This website has some pretty good instructions for checking the headlight vacuum system. Look for the link at the left hand side of the page, Vacuum Trouble.
Instructor
Joined: May 2006
Posts: 223
Likes: 1
From: Kennesaw GA
I just replaced all of my hoses and the headlight relay, only to find out that I have a leak in my vacuum cannister under the master cylinder. The best bet is to follow the instructions on corvette-101.com, they have everything there to help you troubleshoot the issues and find the problem.
While you have a guage to test vacuum, pull the middle (yellow stripe)hose off of the headlight relay (this is the source) and see what you are reading there. If it is lower than what you have at the manifold, you know there is a problem with the cannister, the hose or the 'T' fittings near the manifold. If it is the same, then you need to leak check your relay and actuators to see if one or both of them are causing the issue. Again the instructions on corvette-101.com are the best.
While you have a guage to test vacuum, pull the middle (yellow stripe)hose off of the headlight relay (this is the source) and see what you are reading there. If it is lower than what you have at the manifold, you know there is a problem with the cannister, the hose or the 'T' fittings near the manifold. If it is the same, then you need to leak check your relay and actuators to see if one or both of them are causing the issue. Again the instructions on corvette-101.com are the best.
