I have a question regarding my headlights operation that I hope someone will be able to answer...despite my poor description of the problem...Here goes...


The headlight will only raise when I little black rubber hose w/ a plug on the end is pulled out of what I believe is the vacuum line? They will only go back down if I put the little rubber hose/plug back on.

Any ideas? They seem to be working fine a couple of weeks ago...and the shop I had it at believes that the two canisters work fine. Is there a new part I need to order??

Thanks in advance!!

Michael

 

Go inside the car and pull the over-ride switch **** down (D below). The lamps should pop up. If they do then I would take a hard look at the headlamp switch.

Essentially what you are are doing is removing vacuum from the small hose side (hose A) which is what keeps the headlamps down. When you don't have vacuum on this hose the piston in the relay (D below) drops and switches vacuum to the up side on the large hose (P below)

You can check this by going to the relays under the header bar and pulling hose M or N off.. when you do this one side should open up.

 

Thanks so much...where do I find the over-ride switch inside the car?

Michael

 

under the dash right under the steering column.

 

Order an owner's manual. It makes a good explanation of how things work on your car, including the headlight override.

 

Some good news...got to drive the car some more today and test out everything on it....well, the headlights do work and pop-up...however, it takes about 45 seconds...they go down within 2-4 seconds. Any ideas on what would cause such a delay to come up? Of course, this engine is making a lot more power...about 3 times as much, and has an aggressive cam in her...perhaps that is the culprit??

Thanks
Michael

 

canuck9 it is not creating enough vacuum.

 

Use Willcox's diagram and this troubleshooting guide and you will find the problem.
http://www.corvette-101.com/vacuum.htm

 

What would I do if I had a slow system...?

First I would install a vacuum gauge in the system with the car running. I would then shut off the car and see if the vacuum bleeds off. You would need to do this on both the large and small hose side.

If the vacuum holds then you know the issue is the camshaft.
If the vacuum drops then I would go looking for the component item(s) dropping (leaking) vacuum.

I would then take a hard look at each hose connection looking for cracks in the hoses. If you have cracks there is enough hose to most items that you can cut about 1" from the hose and re-attach it.

If the problem is still there:

I would next check the "check" valve at the intake manifold and make sure it's holding vacuum.

I would then move to the actuators and test them (there is a video on our site for this). If you test them from the non-rod (front) side and they leak you must replace them. If you test from the backside (rod side) and they leak you can usually fix them with a seal, boot and retainer kit.



If the actuators hold vacuum, I would then move to the relays... test both sides small and large hose side.

If the relays are good, then move on to the next item.. I think this video will help you understand how to test each item, it’s just finding out which one it is.



Now one thing I’ve overlooked, is the slowness could also be caused by failing bushings and pivot bearings… Usually these things work for a long time and the failure is almost always one of the component vacuum items.

Willcox

 

Great stuff...thanks so much!! This is why I love this forum.