'79

Problem: Right (passenger) headlamp assembly starts to rise about a second after the left side. The delay between operation is more noticeable with the engine at idle and also the passenger side is slower and might even pause for a moment with the engine at idle. Cruising at moderate speed finds them both opening nice and quickly but still the delay before the passenger side begins.

What I've done so far:

1) All moving parts nicely cleaned and lubricated. Nylon bushings replaced. Did not replace bearings as they seem fine and I also wasn't sure how to remove them I did not remove the entire assembly as I couldn't figure out any reasonable way to remove them through the top. The springs on the driver side look significantly newer; otherwise the mechanisms seem to have all original parts. Both the actuators and relays had been replaced before my ownership.

2) While I didn't measure the force to manually open them (perhaps a fish scale would work?) they both operate freely, quietly (except the audible "snap" when locking open) and with similar effort.

3) Actuators replaced. Two (both right side) arrived with catastrophic leaks.

4) Every component checked for leaks. All of the hoses, the check valve and the vacuum tank hold quite high vacuum (say 25 inches) indefinitely--think days. The headlight switch, override switch and associated control hoses also hold vacuum indefinitely while connected to the relays. Both actuators (in both open and close modes) have slight leaks at higher vacuum. Both relays [seem] to have slight leaks while switching positions and also in the "open the unit" position. If I operate them immediately after shutting off the engine I can get an open and nearly complete close cycle. (I say nearly complete because while they look fully closed one or both will pop back up after an overnight sit.) After a few hours (or even days) the driver side will pop up a bit but nothing more. They do not pop up by themselves even after weeks provided they were closed with the engine running or immediately afterwards.

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Questions:

1) Am I correct that I can identify either the passenger side mechanism or relay is a significant part of the problem by switching the relay positions? If the driver side is now delayed it's the relay that's most of the problem; if the passenger side is still delayed then it's time to do more investigation of the mechanism?

2) Is there any sense to replace the vacuum hoses involved in the actual operation? Again, I've checked them off car and find that they hold high vacuum indefinitely but is it possible that the ends have stretched somewhat over time and now allow minor leaks at the connections? (The entire control system with the smaller diameter hoses was checked on-car and it holds high vacuum indefinitely.)

3) Am I also correct that slight leaks and/or DOA units, and/or rapid failure and/or short life are essentially the norm with the crap that is the currently available actuators and relays?

4) Should it come to headlamp assembly removal any suggestions for doing so? I have FSM and AIM but they are not particularly useful in that regard--especially when it comes to removing them from the top.

 

Slow headlight rising usually indicates a leaking rod seal of the actuator and its best to reseal both of them at the same time. If I recall correctly the seal kits cost around $20 and all the Corvette vendors stock them.

 

Thank you. I've read that here before even if I don't quite understand how a leak at rod seal slows opening as it sure seems to be on the other side of the diaphragm and would only be a problem during closing. Please enlighten me!

Also it seems more a problem of delayed operation of one unit than "slow". Once the passenger side starts to rise (no more than one second) after the driver side it usually* pops up and snaps locked just as quickly. All totaled both lights are up and locked in less than three seconds--they just don't do it in unison which I [think] is a hallmark of a perfectly functioning system.

*after sitting for a while and a start with nothing but idling the passenger side unit sometimes pauses for a split second during its rise.

 

The headlights will never rise and fall together because they're not mechanically tied together. The front of the actuator (rod end) is the end that pulls them open and the rear end of the actuator pulls them closed.

 

Please excuse stupid me confusing in/out, pressure/vacuum and upside-downside Yes, the operating link comes forward to open the mechanism so that shaft boot is part of the seal when opening! What was I thinking???

 

I've thought of that but from my research--before making this post--I was under the impression that the eventual different length operating vacuum lines for relays/actuators and eventual flip-flop between left and right actuators were due to an evolving system designed to open and close the headlamp units as close to military precision as possible.

I did ask about flip-flopping the relays but I believe that due to different length lines that I can't just move the hoses and have to move (or at least unmount) the relays.

 

Mike,
just went through this enduring endeavor myself on my 68.
They will come up and go down in synch with one another if the system is leak free.
Operative is leak free.
Allot of experience here so ask away.
As Alan pointed out the cheapest and most likely culprit will be a relay.
Disconnect and swap the center hose on the relay (yellow stripe).
If the oposing HL works then the relay is tired. The center dog bone seal leaks over time.
Dave on the forum here can rebuild them. Stay away from after market ones.
You can by 10 and 9 could be leakers out of the box.
Have the orig. ones rebuilt by Dave.
Next you will need a miti-vac hand pump.
This is to check the HL actuator in ?
If the relay is not the issue you will need to test the actuator.
If it is leaking at the front line port(green line) it can be repaired.
There is a seal and a witches hat shaft seal that can be replaced.
Again if orig. actuator rebuild it or have it done. After market ones same problems with leaks right out of the box.
If it is leaking to the rear, lowering port(red line) the internal diaphram is shot.
It will need to be replaced. Try and find an orig they pop up from time to time.
If the problem is beyond the relay/actuator then we will continue to trouble shoot.
Let us know how you make out.
I went through everything till I was cross-eyed only to find out I had a leaky brand new actuator and a failing HL switch.
When the system is tight both HL's will snap and pop like
a Marine Drill Team.
Marshal

 

Thank you very much Marshall! I did believe that the engineers really sweated getting those headlamp doors to open in nearly perfect unison despite not being physically attached to one another.

I do have a MiteeVac and find indispensable for a working on an old C3!!

I'm certainly aware of problems right out of the box! Two of the right side actuators had HIDEOUS leaks as received. I'm certain that the actuators that were in the car when new to me were non-OEM replacements. I'm certain that the relays had been removed and nearly certain they were replaced--probably non-OEMs as well.

After the first time I replaced the actuators to suspect everything but the new parts I learned to test new parts with the Miteevac BEFORE installation!!! The new actuators definitely have minor leaks. I can't remember if all four ports (of the two actuators) or only three are leaking but I do know that everything will hold high vacuum for at least 5 minutes with very little loss. The same is pretty much true for the relays--some very slow leaks but nothing approaching major.

These are the things I know for certain are leak free (will hold vacuum for days):

1) The entire control circuit to include the headlight switch, override switch and all of the small tubing while attached to the relays.

2) The large vacuum tank.

3) All of the hoses (tested when removed from the car).

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While individual leaks are small, when everything is together the operating portion of the system (again the control portion is tight) looses vacuum within a few minutes. Well--it will hold 5 inches or so of vacuum for hours if not days but if you wait to turn off the lights for more than a few seconds after shutting off the engine, the doors will close but one or both will probably be up the next morning. Wait more than a few minutes and you get nothing...

As long as the lights are shut of with the engine running the doors will not open no matter how long the car sits. Once I got the system working like it is I have never seen the lights "wink" on engine start-up. I had to replace the headlight switch (fried dash light rheostat) and the replacement rapidly developed a vacuum leak. I took it apart, used some silicon grease, carefully reassembled and it's been fine for months.

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I'll start some substitution tests on the relays soon to see if I can get the driver door to be the one that opens later.

Until then I have a question for you:

Do you know if the vacuum lines can leak at connections? I'm pretty sure that the lines are original to the car--if not they're very good quality replacements as they have nice thick walls and the correct striping. While still reasonably soft they're no longer as subtle as I would expect new ones to be.

 

do you even drive this car?

 

Hi S,
No, not now.
But I've driven it a bit more than 46,000 miles.
Regards,
Alan

 

Lets take your ? 1st.
Yes, they can leak around the connections.
As Alan had taught me cut the ends back 1/2".
This should give you fresh hose at the connection.
Just make sure you check the length before you snip.
I replaced all hoses. The control lines under the dash are
a joy to change

The HL's when closed will remain closed after you shut off the car.
They need the control side of the relay to divert vac to the front port.
Even if the vac leaks out 5 min after the car is turned off the lights
will remain in the last position they were in when vac was applied.

Here's what I did.... I checked the relays, then actuators, then the lines
back to reserve tank, reserve tank, check valve, control side.
When they all hold vac the system will bedazzle small crowds at
cruise nites. They'll think your Wiily Wonka when you demonstrate
those lights and wiper doors.

Allot of good reading from past threads. I learned allot from reading and Dave was a big help.
The winking head light and dancing wiper door is associated with a
leak on the control side. The vac reaches the large center yellow stripped line on the relay before the control side can raise the piston
inside the relay.

My car produces 19 inches of vac. The system when leak free per miti vac testing can begin moving with as little as 5 inches when tight.

Hope this helped.
Marshal

 

Hi S,
No, not now.
But I've driven it a bit more than 46,000 miles.
Regards,
Alan[/QUOTE]

Hey S,
Alan has his red one parked for the season.
He's driving the one in his avatar now
Marshal

 

Thank you again marshall135!

I'll try cutting back the lines 1/2" or so at each end.

I already suspected that replacing the control lines through the firewall would be an interesting experience but again everything involved in the control part of the system holds 20" or so of vacuum indefinitely--while attached to the relays. If I decide to replace the operating hoses (I can't remember the name but found what is considered "the" source for such) I'll order a complete set.

Your explanation of the causes of rising and "winking" units is exactly what I thought--related to the control side. They will rise if the entire system runs out of vacuum before the down cycle is 100% complete and "wink" upon start-up if you have a big-time leak in the control system. Correct?

BTW, I continue to be amazed by pictures like the ones you posted in this thread. It appears as if it just rolled off the assembly line!

I can live with surface rust on non-structural things but I DO want my headlights to work as close to perfect as I can get them... I was a kid and early teen during the C3 era and the thing I most remember about them (my favorite uncle bought a number) was the headlight operation. I remember the acceleration of his '69 L71 but I was less than 10 and it didn't seem as quick as a jet taking off--much less the rockets that I so wanted to ride--so I wasn't completely impressed.

 

Go to the link below...Wilcox Corvette has a video on diagnosing a headlight vacuum problem....Good luck!

http://repairs.willcoxcorvette.com/1...eid=381381c2f8

 

Yes to your ?
A completely emptied absent of all vac system will cause the HL and Wiper door to open upon start up and will close once the system has built up sufficient vac.
The wiper door closes first then the headlights usually.
The wiper side requires less volume so it responds first to presence of vac.
I just tell folks its going through a diagnostic test prior to driving.
After all c3's are supposed to look like fighter jets inside.
Again once you rule out any leaky components the system should respond smartly.
As for the fabulous photos they were posted by Alan not me.
If you need a picture of just about any component on a C-3
I'll bet Alan has a pic of it.
I keep telling him to produce a pic guide of the perfect C-3 and retire early
His work and pics are both priceless and an asset to all who seek assistance. When he had his car judged they probably opened the doors and hood and said ok 100% time for lunch.
I would love to see his car someday.
Ok ADD kicked in there for a moment back to headlight stuff.
Test the relays and actuators since the control side has been verified and that should be it. I also checked all lines for routing.
Make sure none are pinched in the radiator support or along the drivers side fender.
The hose kit that is supposedly spot on comes from Doc Rebuild.
He is a parts supplier.
The kit I purchased elsewhere supplied control lines black w/white stripe to thick to pass through the fire wall grommet.
Keep asking we got cha
Marshal

 

My first results were unexpected.

I flip-flopped the main supply hoses (from tank to center relay). One was actually a bit too short to do this but it fit well enough for a test. Now both doors rose and fell in nearly perfect unison but overall operation was noticeably slower. While they locked Also after shut-down the system lost vacuum far more rapidly.

I paid more careful attention to the hose ends and discovered that some looked fairly good while others had definitely stretched.

My working hypothesis is that the hose ends are some portion (perhaps most or even all) of the problem. Since more than one are barely long enough (before trimming), it seems I need to replace them all before I can continue troubleshooting.

A new set of Doc Rebuild hoses are on their way. (I'd heard about their products before and did enough research to believe that theirs are, indeed, the best available.)

 

I'm a little late to the party here, but have you tested your relays? Even a very small leak can cause all kind of issues. Also, are yours original GM or imports? Original ones look like this on the side:

 

A little late, but since you did say it works better at highway speed, if the check valve is leaking the headlights will open at different speeds due to lower tank vacuum psi and different resistance in the headlight door springs and moving parts. This is especially noticeable if your cam has a lower idle vacuum.

 

I had the relays out shortly after I got the car as headlight operation was pathetic. Such was one of the first things I did and while I tested them per some good instructions found on the web, I wasn't at the time aware of the wild quality difference between OEM and aftermarket. They tested good but I didn't keep anything under vacuum for more than a couple minutes.

At least three of the fastener heads for the relays just twisted off. It certainly wasn't fun to drill and tap new holes up there I did run my finger along the plastic rim below the metal and feel raised lettering exactly like in the photo so I suspect they are OEMs.

The check valve tests perfectly and holds vacuum indefinitely.

I'll continue the thread after the new hoses arrive and are installed. Here's hoping that such proves to be the vast majority of the problem.

I still have some difficulty determining what is and is not original to this car. I haven't found any modifications but I have found plenty of evidence of previous replacements/repairs. Some of the repairs were done very professionally using OEM parts--others are quite amateurish using poor quality aftermarket parts.

 

There have been very few original GM headlight relays I have tested that were still good and vacuum tight. Even a small leak can cause problems. If you want to use my method I have attached a couple of videos below. These tests are with the assumption the top control chamber is vacuum tight (most are).