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Headlight/wiper cowl vacuum questions, 1972

 
Old 12-02-2018, 10:42 AM
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ivanh3
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Default Headlight/wiper cowl vacuum questions, 1972

I inherited my dad's 1972 Corvette, It was his daily driver for over 30 years but in his last year he didn't drive it so much and about four months prior to his death, he hit a concrete barrier in a parking lot at low speed. The impact was on the front passesnger side and bent the bumper in about 2-3 inches. Thanks to some help here, I was able to rebuild that front part.

After the accident, my dad kept the headlights in the up position because (I thought at the time) they couldn't go down due the fiberglass nose being pushed in some and interfering with the travel of the headlight assembly. I was able to fix that somewhat and even tried to recenter the headlight by loosening the three nuts on one side of the headlight. That somewhat worked. It it sill not centered like the drivers side, but the assembly seems to move by hand with little resistance.

Here is where I am now:
The headlights and the cowl will not move at all if the vehicle is turned off.
If the vehicle is on, and the lights are off, the wiper cowl works fine.
If the vehicle is on, and the headlights are on, the wiper cowl will not open fully, and the wipers will not work.
If the vehicle is on, and the wipers are off, and I turn the headlights on, the driver side goes up (a bit slow), and the passenger side, will try to go up. Sometimes it doesn't work, and if does, it is real slow.

When I was adjusting the headlight assembly in an attempt to re-center, I did not feel that its movement was hindered. I don't think (but I am not sure) it was damaged in the accident.
I have ordered a Mityvac to begin troubleshooting. There are some good threads here on how the system works. Am I correct that the vacuum/air tank is to allow the system to work with the motor off? Also, are the headlights supposed to "lock" when they are in the up position? Any other guidance will be greatly appreciated.
Ivan

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Old 12-02-2018, 01:06 PM
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Originally Posted by ivanh3 View Post
I inherited my dad's 1972 Corvette, It was his daily driver for over 30 years but in his last year he didn't drive it so much and about four months prior to his death, he hit a concrete barrier in a parking lot at low speed. The impact was on the front passesnger side and bent the bumper in about 2-3 inches. Thanks to some help here, I was able to rebuild that front part.

After the accident, my dad kept the headlights in the up position because (I thought at the time) they couldn't go down due the fiberglass nose being pushed in some and interfering with the travel of the headlight assembly. I was able to fix that somewhat and even tried to recenter the headlight by loosening the three nuts on one side of the headlight. That somewhat worked. It it sill not centered like the drivers side, but the assembly seems to move by hand with little resistance.

Here is where I am now:
The headlights and the cowl will not move at all if the vehicle is turned off.
If the vehicle is on, and the lights are off, the wiper cowl works fine.
If the vehicle is on, and the headlights are on, the wiper cowl will not open fully, and the wipers will not work.
If the vehicle is on, and the wipers are off, and I turn the headlights on, the driver side goes up, and the passenger side, will try to go up. Sometimes it doesn't work, and if does, it is real slow.

When I was adjusting the headlight assembly in an attempt to re-center, I did not feel that its movement was hindered. I don't think (but I am not sure) it was damaged in the accident.
I have ordered a Mityvac to begin troubleshooting. There are some good threads here on how the system works. Am I correct that the vacuum/air tank is to allow the system to work with the motor off? Also, are the headlights supposed to "lock" when they are in the up position? Any other guidance will be greatly appreciated.
Ivan
You must have vacuum of a sufficient amount in order for the system to work. You should try to check each hose connection for leaks. That tank is there to store vacuum which I believe helps the system keep the wiper door and headlight doors closed while the car is running and when it is off. As far as operating the system when the car is not running, I believe you should be able to close the wiper door and/or headlight doors after the car is off but I am not sure the tank will hold enough vacuum to allow you to open those doors, I don't think it is designed for that. Some things I would check while waiting for your MightyVac are the vacuum filter and vacuum check valve. The headlights have a lock position when open. It sounds like that pass side light might still be getting mechanically stuck...

If the vehicle is on, and the headlights are on, the wiper cowl will not open fully, and the wipers will not work. There may not be enough vacuum. Or the check valve and filter might not be functioning. The filter is there to keep contaminants from entering the engine. The check valve allows vacuum to each system and keeps the system from losing vacuum, a one way valve so to speak.

Here is a helpful article about the vacuum system and keep perusing the forum for more information on the system. Willcox also has lots of help on those two systems on their website.

http://www.corvette-101.com/vacuum.htm
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Old 12-05-2018, 10:12 AM
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This morning I did some troubleshooting with the Mityvac.
On the driver's side, I disconnected the hose from relay that goes to to the rear actuator nipple and pumped it up to 20mm of vacuum. It held with no needle fluctuation. Reconnected hose.
I then disconnected the hose from driver side relay that goes to the front actuator nipple and pumped it up. The headlight raised. Both front and rear hoses from relay to actuator were tested and held vacuum.

On the passenger (problem side) I repeated the same test. The rear hose from relay to actuator is good but connected to actuator it would not hold vacuum and I could not get the headlight to raise by applying vacuum to the front. The gauge never read above "zero".
So does this mean bad actuator? It seems there is leak somewhere because I can not get the windshield cowl to fully open while headlights are up. This seems the likely cause.
If this is the case, however, why do both headlights close with no issue when I turn the headlights off?
When headlights are off is less vacuum being utilized and that is why the wiper cowl works better?
Ivan
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Old 12-05-2018, 11:30 AM
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Now that you have the proper tool you can test the entire vacuum system and all it's components.

The rear hose from relay to actuator is good but connected to actuator it would not hold vacuum
If the rear actuator port will not hold vacuum the actuator is toast. There are a few re-builders out there that can disassemble and make the repair, but it's pricey. If the actuator needs to be replaced, make sure it's from a reliable source like Willcox. Your quote of " why do both headlights close with no issue when I turn the headlights off?" tells me that the rear port is indeed holding vacuum otherwise the door probably wouldn't close.

I could not get the headlight to raise by applying vacuum to the front. The gauge never read above "zero".
By far the most common issue of the door not opening and NO vacuum is the front seal is torn/missing/toast. The good news is the seal can be replaced. If you search Willcox's tech site you will find valuable information on how to accomplish this.

While you are testing the the actuators again, test the relays internal seals. Easy to do. Disconnect the vacuum hose to the middle port on the relay and connect the Mityvac to it. Then disconnect the lower relay hose and block it (finger, blocked hose section). Pump up the Mityvac and observe the gauge. The relay should hold vacuum.

After you get the headlights up to speed, I can help you with your wiper door if needed.

Regards, Dave
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Old 12-05-2018, 11:47 AM
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Thanks for the response. When I connect the mityvac to the rear port on the passenger (trouble) side, I can pump the needle up to 20, but it slowly drops. I tested the hose separately and it completely holds. This same test on the good side held vacuum with no movement of the needle. Could there be a small leak on the back side and that is why it will still close?

I am going to just replace the whole actuator. It looks like a fairly simple install. I am hoping that this may, in turn, fix the wiper cowl, as it works perfectly if the headlights are off. Maybe that leak on the front side right actuator is bad enough that it weakens the whole system?
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Old 12-05-2018, 12:32 PM
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Could there be a small leak on the back side and that is why it will still close?
Short answer, yes. A very small leak can still operate the actuator. It's the big ones that cause trouble. Be careful ordering a replacement actuator, many of the Chinese imports leak right out of the box. This may be redundant, but are you connecting directly to the actuator or through the vacuum hose from the relay?

Maybe that leak on the front side right actuator is bad enough that it weakens the whole system?
Indeed. Every vacuum hose is connected together in some way or another. Remember this, it's not the vacuum sucking the internal diaphragm into position, it's the atmospheric pressure on the other side of the vacuum pushing the diaphragm. When you have a leak, you are essentially reducing the pressure difference between the two sides by allowing atmosphere into the low (no) pressure side.
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Old 12-05-2018, 01:06 PM
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Originally Posted by Dave J View Post
Short answer, yes. A very small leak can still operate the actuator. It's the big ones that cause trouble. Be careful ordering a replacement actuator, many of the Chinese imports leak right out of the box. This may be redundant, but are you connecting directly to the actuator or through the vacuum hose from the relay?
I connected both directly and through the vacuum hose from the relay on both sides. The side in question has a slow drop on the back side (about 2 minutes from 20 mm to 0) and I can't even get it to register on the front side. The good (drivers) side holds both direct and through the hose.

I did see a recommendation/opinion regarding the quality of replacement actuators, but I almost certain that these are already replacements and not original. I seem to recall my dad telling me that he had them replaced.
I will probably replace. I will check prior to install. My medium term plan is to replace the vacuum system with an electric one. Will probably leave the cowl alone.

Ivan



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Old 12-05-2018, 02:17 PM
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Just found these two electric headlight conversion kits on eBay. Someone had one for sale on this forum which is how I found out about it and the Full Throttle I found through a search. Both get good reviews on eBay. I have asked for installation instructions from the first. We will see. If anyone has any experiences/opinions with these, would love to hear them.

C3 Corvette Electric Headlight Motor Conversion Kit

Full Throttle Corvette Conversion Kit

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Old 12-23-2018, 07:14 AM
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Ended up putting in the kit sold by Richard454. Fairly easy install. Very happy with the purchase. Thanks Richard! Now I need to figure out what vacuum lines I need to plug and fine tune the adjustment of the headlight assemblies, but this is way cooler than the vacuum system.
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Old 12-23-2018, 09:22 AM
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To remove and block the vacuum lines running to the headlamps.

Remove yellow 6 from the vacuum tank and plug the port, then remove the green hose 4 from the T at the vacuum tank and plug the open port on the T. Then remove the black/white stripped hose from the T at point A... and plug the hose.

Willcox

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Old 12-23-2018, 12:59 PM
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Here is a short video of how it looks now. I am going to replace the clevis sleeves, some bushings, the rear pins, and springs since I have the hood off and the access is easy. I still need to fine tune the assembly in terms of position, but I won't do that until the new parts are installed.


Thanks again for the help,
Ivan
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Old 12-28-2018, 09:02 AM
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Originally Posted by Willcox Corvette View Post
To remove and block the vacuum lines running to the headlamps.

Remove yellow 6 from the vacuum tank and plug the port, then remove the green hose 4 from the T at the vacuum tank and plug the open port on the T. Then remove the black/white stripped hose from the T at point A... and plug the hose.

Willcox

Thanks for the diagram. I am going to run this down today. I finally found the tank!

Would there be any difference in plugging the lines off at the front of the car? That tank is hard to get to.

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Old 12-28-2018, 10:46 AM
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You could plug the yellow and green hoses at the relay too... Yes..
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Old 12-28-2018, 04:28 PM
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Just for clarification the vacuum tank is to aid in opening and closing the wiper door and headlights while the engine is running. It keeps the engine from supplying the majority of the vacuum while running. It should store vacuum to allow the owner to open and close both systems a few times when the engine is not running. I'd say 99% of the C3's today cannot do that due to small leaks.
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Old 12-30-2018, 03:08 PM
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Originally Posted by Willcox Corvette View Post
You could plug the yellow and green hoses at the relay too... Yes..
I ended up doing this pretty much like you recommended: I plugged the opening for the yellow hose at the tank and the green line at the "T". The black/white smaller hose for some reason had a connector about 6-7 inches from the firewall. I think a portion of the hose had been replaced. So I just plugged off the hose at that connector. Now there are no vacuum hoses in the front of the compartment that were involved with the headlights. I also pulled the vacuum relays out and adjusted the headlight assemblies. In fact, I used your video for guidance to adjust the headlights. Thanks for the input, diagram, and video!
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