Help needed for 1973 Headlights - one closes, one will not

[David C.]

I am a beginner with Corvettes, and have acquired a fairly original 1973 convertible one month ago. The headlights were working (if a bit slowly) when I first got the car, but now the driver's side won't close when the lights are turned off, and the passenger side closes but at times then wants to pop back up some. I know there is lots of information out there on vacuum systems, and I searched the archives, but can anyone point me in the right direction to help save me some time? Where should I start?
Thanks in advance!

[Joe L.]

Re: Help needed for 1973 Headlights - one closes, one will not

I am a beginner with Corvettes, and have acquired a fairly original 1973 convertible one month ago. The headlights were working (if a bit slowly) when I first got the car, but now the driver's side won't close when the lights are turned off, and the passenger side closes but at times then wants to pop back up some. I know there is lots of information out there on vacuum systems, and I searched the archives, but can anyone point me in the right direction to help save me some time? Where should I start?
Thanks in advance!

David------


The first thing I would check is the driver side headlight actuator. If you find that's the problem, a new actuator shaft seal might solve it. Of course, you also want to check all the vacuum lines to determine if any are obviously failed or have slipped off their fittings.

[Michael W.]

Re: Help needed for 1973 Headlights - one closes, one will not

David-

There is a significant vacuum leak somewhere in the system. It might be at the actuator as Joe suggests but don't be surprised if there's several small leaks adding up to one big one. Each needs to be repaired. There is no quick and easy fix to get the system working as designed. Start at the vacuum source on the intake manifold and test each component in isolation and in sequence for functionality and leaks.

Don't forget that the HVAC is also vacuum driven and on the same circuit as the headlights.

[Jim T.]

Re: Help needed for 1973 Headlights - one closes, one will not

Headlight vacuum operation trouble shooting is available in the archives, however to easily put your headlight down after you turn off the car is to reach underneath the headlight finding the metal elbow and just pull down at the elbow, the light should go down. You may hear air/vacuum when it is going down. If it does not easily go down you may need to check out why. With the engine off and vacuum storage tank empty of vacuum, operation of raising and lowering the headlights should be easy manually.
Vacuum operation of headlights when my 1970 was new would last without engine operation the next day.

[Alan S.]

Re: Help needed for 1973 Headlights - one closes, one will not

Hi David,
If you have a small vacuum pump with a gauge like a Mity-vac you can test the headlight actuators.
You'll see 2 ports on the actuator… a green striped hose on the front straight port, and a red striped hose on the rear curved port.
First, plug the rear/red port and attach a hose from your pump to the front/green port. If vacuum holds the actuator's internal diaphragm is ok, if the vacuum bleeds off the diaphragm is faulty and the actuator must be replaced. (Or rebuilt by someone with that capability.)
Next, plug the front/green port and attach a hose from your pump to the rear/red port. If vacuum hold the diaphragm and the sealing grommet are both o.k., but if the vacuum drops off, but was good in the first test, the sealing grommet needs to be replaced. (This one you can do at home.)
If the actuators prove to be operating properly you can next test the relay (s) for the actuators.
Good Luck!
Regards,
Alan

I just also thought to suggest you can reverse the hoses from one relay to the other. If the symptom moves from headlight to headlight too it indicates a relay problem. Just be sure you don't begin to mix up which hose goes where.

[Rex M.]

Re: Help needed for 1973 Headlights - one closes, one will not

My headlights have done similar actions. I laid on my back and shot WD40 on the pivot points and they started working normal again. It's probably the vacuum leaks but it's easy to try.

[Michael W.]

Re: Help needed for 1973 Headlights - one closes, one will not

Vacuum operation of headlights when my 1970 was new would last without engine operation the next day.

It's very very hard to convince newer owners that this is true. Most cars are in such poor condition today that the headlights barely move when the engine is running, never mind many hours after shutdown.

[Tom R.]

Re: Help needed for 1973 Headlights - one closes, one will not

I know there is lots of information out there on vacuum systems, and I searched the archives, but can anyone point me in the right direction to help save me some time? Where should I start?

Place to start is the manifold and from there troubleshoot the entire system, identifying problematic issues throughout the system. Lots of moving parts and to be systematic and restore to full functionality must be patience and test each component. Just completed my 78 by having my actuators rebuilt and now the suckers pop. Let's face it...the vacuum system is forty years old and stuff wears out.

Drop me an email and I will send you a comprehensive troubleshooting guide that includes graphics in a step by step procedure. It's tedious but thorough...there isn't anything that is quick about it but it is satisfying once you have isolated the problems areas.