While trying to chase down a vacuum leak on my 79 I believe that I have found out that both the actuators have defective diaphragms. When I put vacuum on the hose with the green stripe neither one will hold any vacuum. But when I put vacuum on the red hose the pass side will hold vacuum, but the drivers side won't. So have I made a correct guess. Can these be rebuilt? Thanks Gary B.

 

Don't know the answer....but I might have similar problems...so I'm bumping for ya...ttt

 

Are you using a vacuum tester? One of the hand-held deals with a vacuum gauge? If so, and it is holding no vacuum in either direction, the actuator is no-good. I don't know if they can be rebuilt or not, but I have never seen a kit to do it. I just went through the whole system on my 69 and found a bad windshield door actuator that was doing just what your headlight is doing (OK one way, no vacuum the other way). Replacing it fixed the problem. The 69 has the same system as yours for the headlights, so I'm assuming the diagnosis is the same.

Hope that helps.

 

I don't think you test them that way. The system is set up with vacuum relays and that works the actuators one way or the other. As far as tracking you leak I would first get a vacuum reading as a base line then plug the red and green lines to the actuators and see if there is a difference. If not check the vacuum storage tank the same way. (a common problem on early C3s) AL.

 

A Guy named Chris Prowl wrote a complete testing troubleshooting and Fix guide for C3 Headlight & wiper doors....its only 10 bucks and is available
I believe thru Ecklers of Mid America... Or you could Ping him over at the C3 registry at (www.C3vr.com)....

He gave it away free for a short time after he wrote it then sold the rights
to one of the vendors... ITS GOOD...

Bob G.
64 72 & 98 Ragtops
76 & 79 Coupes

sorry if I offended anyone by giving out the C3 site...ITS NOT FREE anymore ...BUT trail memberships are available...which is long enough to get some answers ....

 

Are you talking about the Headlamp Vaccuum relays? If so I have the directions to rebuild them - I ahve never done it. If this is what you are talking about I will post.

Darrel

 

Darrel: Would you post the instructions to rebuild the relays, I may need that information. I got some trouble shooting directions from Dr. Rebuild and his instructions says to do it the way I did. Gary B.

 

this site has a good section on vacuum trouble shooting. they even have a procedure for redoing your relays. didn't work on mine, but maybe it will work on yours.

try http://www.corvette-101.com

i'm thnking about maybe attempting to cast a new rubber piece for the inside of my relays. i have a book on order about casting small rubber parts. this relay piece may be a good project to try since nobody reproduces them or rebuilds these relays.

the drivers side actuator that will not hold a vacuum on either side is dead. you will have to get a replacement. your passanger side actuator may only need a new shaft seal.

i got lucky with my cans. both of them only needed new shaft seals. the diaphrams were fine on both. my relays are leaking though.

hope this helps,

Mike.

 

Many times it's just the shaft seal and not the diaphram of the actuator that leaks. Those are available through many vendors, along with the dust boots. Changed mine out and the actuators work like new.
Eddie

 

This might help.

http://www.corvettemagazine.com/2002...s/lights-1.asp

 

The pass side diaphram is good and shaft seal should fix it.The drivers side diaphram is bad and the actuator will have to be replaced.Great description of problem!

 

I just replaced my vaccuum relays this weekend. Headlamps snap up and snap down nicely... Sorry the post took so long.

Darrel




Vacuum Troubleshooting

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I decided to put together a vacuum troubleshooting because their just isn't a free one on the internet I could find. I think about every C3 owner out there has had some sort of problem with their headlights opening and closing; and it's not easy to fix them without a good guide. Click on the vacuum system graphic below to enlarge for printing or to save to your hard drive. I suggest using this diagram to ensure your headlamp vacuum system is "wired" correctly before you start troubleshooting. All of the tests should be conducted with the engine off, unless otherwise indicated.

Tools
General Function Test
Vacuum Hoses
Vacuum Reservoir Tank
Vacuum Check Valve
Vacuum Filter
Head Lamp Actuators
Manual Over Ride “Pull Down” Switch
Head Lamp Relay Valve
Head Lamp Switch



TOOLS REQUIRED

Hand Held Vacuum Pump: Used to verify the hoses and vacuum components will hold a vacuum.


Vice Grips: Used to block a hose by clamping it.
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GENERAL FUNCTION TEST
The headlamps should be off and closed and the pull down switch should be pushed in. Pinch closed the small white hose leading to a relay valve and the headlamp doors should open. When released, the door should close. This operation usually can only be performed once without the car running. If this test fails and your headlamps still open and close while the car is running, it simply means the system is not operating at 100 percent as designed. The following tests should help you pinpoint why this test failed.
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VACUUM HOSES
DESCRIPTION: The vacuum system uses different sized black rubber hoses. Small hoses have an inside diameter of 5/32", medium 7/32" and large 9/32". The hoses should have colored stripes that correspond to colored paint dots on the vacuum system components. The colors used are red, yellow, green, white and blue. The red hoses are used to close the headlamp doors and the green hoses are used to open them. Yellow hoses are used for the vacuum supply or holding tank. The small white hoses are signal hoses; they signal the relay to open or close. The small blue hoses are used to connect the pull down switch with the headlamp switch.
TROUBLESHOOTING: First used the diagram above to ensure the vacuum system is "wired" correctly. This includes checking for kinks, pinches and holes. Plug one end of the hose (I use a bolt a little bigger than the inside diameter of the hose) and connect the other to a vacuum pump. If the vacuum pressure drops, the hose has a leak and should be closely examined for damage. If the hose is damaged, replace it. But don't throw it away, you may be able to salvage some of the hose for use elsewhere.
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VACUUM RESERVOIR TANK
DESCRIPTION: The 73-79 models use a long cylindrical steel tank with three brass fittings screwed into the surface that function as large vacuum ports.
LOCATION: The tank is part of the front bumper mounting brackets; therefore a front end accident can cause the tank to fail.
FUNCTION: The vacuum tank provides a source for a vacuum supply when the engine is not running.
TROUBLESHOOTING: Plug two of the vacuum ports and connect the vacuum pump to the third. The tank should maintain a vacuum. If the tank will not hold a vacuum, then it can be replace or possible repaired.
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VACUUM CHECK VALVE
DESCRIPTION: The check valve has 3 vacuum ports; two on one side and one on the opposite.
LOCATION: The check valve is near the rear of the carburetor, close to the intake vacuum fitting on the manifold.


FUNCTION: The check valve enables the vacuum tank to store a vacuum supply when the engine is not running by preventing air from escaping.
TROUBLESHOOTING: The check valve permits air to flow in one direction. Air can only pass from the side with the 2 ports, towards the side with the single port. You should be able to blow into either of the 2 ports opposite the single port. These 2 ports should hold vacuum when attached to a vacuum pump as long as the adjacent port is plugged. The end with the single port should not maintain vacuum pressure and you should not be able to blow air into this port. A leaking check valve may cause the headlamps to open when the engine is turned off; but this depends on the condition of the rest of the headlight vacuum system. A bad check valve, where air travels in both directions, will allow all the air to escape from the holding tank and prevent operation of the headlights while the car is turned off. A clogged check valve will prevent vacuum from being supplied to the system.
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VACUUM FILTER
DESCRIPTION: White plastic with a vacuum port on each end.
LOCATION: The filter is near the rear of the carburetor, close to the intake vacuum fitting.


FUNCTION: The filter prevents contaminating particles from entering the engine.
TROUBLESHOOTING: Hold the filter up to bright light, and look into the ports to examine the filter. If it is extremely soiled, it should be replaced with a new one. Ensure it is replaced the in the same orientation as is was removed or particles in the filter will be sucked into the engine. A cracked or leaking filter may allow dirt particles into the engine, and will cause a vacuum leak.
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HEAD LAMP ACTUATORS Click here for a diagram of internal actuator operation.
DESCRIPTION: Pie pan shaped with a single internal diaphragm attached to a threaded shaft that is visible externally. The threaded shaft is protected by a cone shaped boot. Each actuator has 2 vacuum ports. The front port is straight and identified by a green dot; the rear port is curved and identified by a red dot
LOCATION: Mounted to the rear of each headlamp housing with 4 flanged lock nuts.


FUNCTION: The headlamp actuators open or close the headlamp doors. More specifically, the green hose opens the headlamp doors and red closes them.
TROUBLESHOOTING: Perform the following two steps in order.

1. With headlamps in the closed position, disconnect the large red hose and attach the vacuum pump. If the vacuum pressure holds, the internal diaphragm is good. If the vacuum pressure drops, the internal diaphragm is leaking and the actuator must be replaced.

2. With the headlamps in the open and locked position (if the headlamps will not open normally, try opening them manually by pushing them up from the front underside of the vehicle), disconnect the large green hose and attach the vacuum pump. If vacuum pressure holds, the internal diaphragm and rear sealing grommet are both good. If the vacuum pressure drops, replace the grommet. NOTE: If you do not open the headlamps prior to this test, applying vacuum to the port should slowly open the headlamps until they are completely open. At this point this port should hold a vacuum.
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MANUAL OVER RIDE “PULL DOWN” SWITCH
DESCRIPTION: The manual over ride switch is black plastic push-pull switch with 2 small vacuum ports. The upper port is identified by a white dot and the lower port by a blue dot.
LOCATION: Mounted under the dash near the steering column.


FUNCTION: The headlamp actuators open or close the headlamp doors.
TROUBLESHOOTING: With the switch closed (pushed up) attach the vacuum pump to the blue and block the white port; vacuum pressure should hold. Following this, open the switch (pull it down), a vacuum should still be maintained. If you unblock the white port, you should be able to look into it and see daylight.
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HEAD LAMP RELAY VALVE
DESCRIPTION: Disk shaped steel with an internal diaphragm attached to a black plastic shaft. The upper steel housing has one small metal port connected to a small white vacuum hose. The black shaft has 3 vacuum ports connected to large vacuum hoses. The top port is used to supply vacuum to the actuators to close the headlamps. It is marked with the letter "R" and a red dot; red hose. The center port is the vacuum supply marked with the letter "Y" and a yellow dot; yellow hose. The bottom port is used to open the headlamps and is marked with the letter "G" and a green dot; green hose.
LOCATION: The relay valves are mounted between the headlamps.


FUNCTION: Relay valves control vacuum to the headlamp actuators to open and close the doors.
TROUBLESHOOTING: Disconnect all 4 vacuum hoses. Remove the filter at the base of the relay and inspect it for damage and to make sure it isn't clogged. If it is clogged, the headlamp doors may open slowly.

1. Block off the green port and attach the vacuum pump to the yellow port. Vacuum pressure should be maintained. If not, the relay should be replaced. Failure of this test does not mean the relay will not function at all. What it does mean is that once the car is turned off, the holding tank will not hold a vacuum because the yellow port is always open to the vacuum storage tank.

2. Apply vacuum to the small metal port and note if the valve moves freely up towards the diaphragm. If is doesn’t, the valve is frozen and the relay needs replaced.

3. Release the vacuum at the small metal port. The valve should sharply snap toward the filter end. Slow movement indicates either a worn spring or the valve is sticking. This will cause the headlamp doors to open slowly.

4. Apply vacuum to the small metal port. Pinch off this hose to maintain vacuum pressure and remove the vacuum pump. Block off the red port and apply vacuum to the yellow port. If vacuum is not maintained, replace the relay.
If you this test fails, check out the Headlamp Relay Repair article in A&W's Vette
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HEAD LAMP SWITCH
DESCRIPTION: The head light switch is a push-pull switch with both electrical terminals and 2 small vacuum ports: the front port is marked 3 and the rear port marked 2.
LOCATION: The head light switch mounts in the drivers side dash board.

FUNCTION: The headlamp switch turns the headlamps on and off and signals the vacuum components to open or close the head lamp doors.
TROUBLESHOOTING: When closed (**** pushed in) attach the vacuum pump to port 2 and block port 3. Vacuum pressure should be maintained. When open (**** pulled out), port 3 will not hold vacuum. Attach the vacuum pump to port 2. vacuum pressure should hold.
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Headlamp Relay Repair

After removing the headlamp relay, make a cut with a Dremel on the band encircling the top of the relay, as pictured. Remove the ring and set it aside. Be cautious when making the cut because you are going to reuse the ring during reassembly later.

Remove the top of the assembly and spring and pull the diaphragm from the rest of the relay body.

Use a pair of pliers or cutters to flatten the crimp on the shaft of the diaphragm assembly. Remove the washer and put it in a safe place and then remove the bushing.

Now that you have everything apart, clean all the parts. I used rubbing alcohol. Brake cleaner does a nice job at removing grease and oil as well.

Inspect the diaphragm for tears and dry rot.

Now for the most important part. I've read of several ways of bringing a relay back to life without spending $80 on a new one. My method involves using a rubber revitalizer. I used Rawn Re-Grip www.rawnamerica.com, but similar products exist. A bottle runs for around $5 at any electronics supply store or you can find it online.
The rubber revitalizer restores the elasticity and shape of the rubber. Soak the bushing in it for about an hour. I also massaged the bushing during this period to help work the chemical into the rubber.

After the bushing has soaked for a while, wipe it dry with a clean cloth. DO NOT use alcohol to clean the rubber off at this point. Alcohol will dry it out. Wiping it clean is all you need to do. Try inserting each end of the bushing into the main relay body and see if it fits any tighter. If it does, then your work has paid off.
If you cannot get your hands on rubber revitalizer, try using brake fluid. Please keep in mind that I have not tested this method, so I don't know how well it will work.

Reassemble the diaphragm assembly. Don't forget to crimp the shaft after you put the washer back in place.

Apply petroleum jelly to the bushing and reassemble the relay.
The hardest part of the whole project in my opinion is putting the ring you cut off back in place. You have to work it until it's evenly fit around the top of the relay. I fastened it in place with soldier.

Now the test. Attach a hand held vacuum pump to the large center port and apply about 20 HG of vacuum while blocking the red port. It should hold vacuum. If it works, you are done.