Hi, I have a question about my 69 wiper door. When I shut the car off, about 1/2 a minute later the door slowly opens about a 1/4 inch. When the car is restarted the door closes that 1/4 inch that it opened when the car was shut off.
I did the "15 second test" that is mentioned in another post. When crimping off the small vacuum line downstream of the check valve the wiper door did open. Indicating the vacuum safety switch not doing what it should? What I'm wondering is, if this would allow the wiper door to creep open after the car is shut off? Thanks and take care.

 

I don't know much about the test you refer to. The reason the wiper door opens is because of an imbalance in the two circuits of the vacuum system. The larger hoses are the actuating circuit, they provide the muscle to operate the components (headlight doors and the wiper door). The smaller hoses are the control or switching circuit, they move the vacuum switches internal pistons to direct the vacuum in each actuator.

The biggest culprit in the control circuit is the safety valve at the base of the the passenger wiper arm. If this switch is leaking you have the result you are experiencing.

The simple test is one of two ways;
1 - remove the bottom 2 vacuum hoses from the wiper arm switch and connect them together. You have effectively eliminated the switch. Start the car and observe the result.
2 - remove the bottom 2 vacuum hoses from same switch and with the plunger pushed down, block the lower vacuum port. Connect a short hose to the middle hose and try to blow through it. You shouldn't be able to.
3 - Another test would be to have the plunger in the extended position and try to blow through the middle port. You shouldn't be able to.

If the above tests do not indicate any issues, you have a vacuum leak in another part(s) of the control circuit. The next most common leaking component is the headlight vacuum switch.

 

There have ben several of the new imported valves that have failed. One vendor did a test on several and all were found to be bad. So if you purchase one, it may not be the fix for your problem and may be a defective new valve where a good valve should if the valve is your problem.

 

I agree on the vacuum safety valve at the base of the right wiper arm. Just so you know this keep the door from crashing on the wiper arms until they are fully parked.
There is a small adjustment but if you get it too high the door can hit the wipers even when parked. It's kind of a pain to get to. The best way is to take the grill in front of the wiper door off.
You can manually move the wiper door by removing the rubber plug on the end of the actuator and sticking your finger into it and push. Some say use a screwdriver but I've always been afraid I'd somehow puncture the diaphragm.

 

Have you replaced any parts for the wiper vacuum system???

DUB

 

Hi. No haven’t replaced anything. To be honest it might of been doing it all along and I just wasn’t observant.

 

Thank you for responding to my question.

All of the Corvettes I have worked on that have this problem I know it has everything to do with vacuum leaking out way too fast. there is a controlled bleed area on the vacuum solenoid behind your tachometer that should have a small square cube of foam on it.

If you have an A/C equipped car. Take a look at this thread and take a look at post #13.

https://www.corvetteforum.com/forums...d-problem.html

And when it leaks out to fast....the small control vacuum hose that is attached to the small port on your actuator relay looses vacuum...thus...causes the valving in it to change directions...which will cause the wiper door to open.

You might need to do as Dave advised and preform some tests. But do not be surprised if you have vacuum leaks in other areas not mentioned....such as the thread I did some time ago that is below.

https://www.corvetteforum.com/forums...nk-repair.html

Also..if you have Air Conditioning...you may have other vacuum leaks in that system. But the vacuum to your A/C vents in your car can be detached and that port capped off for testing purposes.

I seriously doubt you have a catastrophic vacuum leak due to it takes so long for the wiper door to come up after you shut the engine off. But these threads are worth looking at so IF you do run into it getting worse and worse...it might shed some light on where you may have an issue.

DUB

 

To my knowledge, that exhaust vent on the wiper switch/solenoid is 'just' a vent...don't know of any 'regulated' venting for that port. When the wiper switch turns off, vacuum in that line is vented through that port. The foam piece placed on it is to prevent any dirt/debris from entering that port when vacuum is turned off (and air is sucked into that port).

 

FWIW: The reproduction wiper door safety valves are known to leak, causing symptoms you describe. Yours may be an original which is worn out or aged, or may be a reproduction?

Here are a few videos showing how to test, demonstrating how the reproductions leak.


Willcox offers a replacement switch which holds vacuum.

https://willcoxcorvette.com/corvette...t-really-works

 

With all due respect BB, do not use the top video, use the Willcox video. The first video tests the wrong vacuum port. Source vacuum is not applied to that port in real life applications.

You may also find this one useful;

 

FACT:

I can tell you this FROM EXPERIENCE!!!!!

These vacuum switches can be made differently on how they vent....because they DO VENT off vacuum when pressed. IF they did not vent off vacuum. Then the vacuum source going to the actuator relay would ALWYS have vacuum on it...thus not allowing it to switch position.

Because I have found that switching the red striped hose with the white striped hose on where they are supposed to be put into the vacuum switch makes them work correctly.

So the main thing is you need to verify the vacuum switch and if it is like GM design or not.

DUB

The reason I KNOW this is.... Dave. I have one of yours and one of Lone Stars and the hoses for Lone Star ones needed to be swapped to make it work.

 

FACT:

I can tell you this FROM EXPERIENCE!!!!!

These vacuum switches can be made differently on how they vent....because they DO VENT off vacuum when pressed. IF they did not vent off vacuum. Then the vacuum source going to the actuator relay would ALWYS have vacuum on it...thus not allowing it to switch position.

Because I have found that switching the red striped hose with the white striped hose on where they are supposed to be put into the vacuum switch makes them work correctly.

So the main thing is you need to verify the vacuum switch and if it is like GM design or not.

DUB

The reason I KNOW this is.... Dave. I have one of yours and one of Lone Stars and the hoses for Lone Star ones needed to be swapped to make it work.

 

DUB:

With all due respect sir, Can you tell me then is it the function of these vacuum switches to vent the vacuum present in the circuit then? Surely a man of your experience can tell us that.

With all due respect.....DUB.

 

I believe the valve applies vacuum to the vacuum relay port in one position, vents the connection to the vacuum relay port in the other.

May be interesting to see what's inside one of these switches. I've only opened the valve portion of a vacuum relay.

 

I would test the components , but that is just me ...

 

Thanks to everyone who has replied and helped me. I think I will test the operation of the safety vacuum switch at the right wiper. By the sounds of things it appears to fail often and is certainly easier to get to over the solenoid at the back of the tach. Thanks again and certainly didn’t mean to start a conversation that would “ruffle any feathers “. Take care

 

Okay... this is as always a funny subject for me.... and I’ll try to explain.

The top video above is not correct and I say this because the imported valves were designed to just block on the lower port and while they may do this just fine, they leak between the middle port and the top vent.....

The issue... is the vacuum must be blocked on the middle port without any leaks for the system to work and function properly. The imported valves were made to just block the vacuum on the lower port only (that’s where it gets funny, because they only work part of the time) and so when the car is on the road if the wipers are in motion you will have a vacuum leak and not to mention the fact that they will also bleed off vacuum when sitting still.

I know some of you might have a sore spot about this because you purchased the imported valve, (we won’t sell it) but it was made with good intentions.

So what I find funny about this is that the company that imports the valves saw me at a swap meet a few years back and told me my video was incorrect and that he was designing the new repro valve to match the test function done on the top video… Major mistake…. I cracked up laughing and pulled the vacuum schematic to show him that the top video was not the correct way to test the valve…. So all they designed the valve to do is block from the bottom port... without any blockage between the middle and the vent.

If you view the schematic below you’ll see the input vacuum is on the middle port… and the middle port is what needs to block and hold vacuum… YOU MUST TEST FROM THE MIDDLE PORT! And it must block vacuum without any leaks. And while the top video is a good attempt to publicly show the valve function and how to test it…. It’s WRONG!

The valve when the arms are closed should pass vacuum from the middle port to the lower port without any leaks.

The valve when open should block vacuum to the lower port without any leaks.

So looking at the late vacuum schematic below you'll see the source vacuum is the red hose going to the wiper relay.

IMHO,

Willcox

 

Hello, I went through 3 different actuator relays (two from Amazon and one from Zip). As Willcox stated, all of them are imported from China and leak vacuum while the windshield wiper operates. Most people do not notice because they use a vacuum from the engine. I have a vacuum pump that works non-stop due to a vacuum leak. Where do I buy the correct actuator relay that does not leak? Looks like Willcox is out of business.

Thank you!