PUNISHER VETTE

Not sure if it's normal or not but it seems every time I start my 69the wiper door opens a slight bit then closes.

The door works great and sometimes the wipers work but not ever time. I've got the rest of the week off so i guess i can try and figure out why this is happening. Anyone had a hind on narrowing down why the wipers work only intermittently?

1. Why does the door open/close upon start up?
2. Best place to start for intermittent wipers?

Derrick Reynolds

Late last year, I got a vacuum leak. Laziness caused me to not diagnose and fix until earlier this summer. Once fixed, the engine is running better than ever, the vacuum components work great, but my wiper door started opening upon start-up. Other folks here recommended I test the check-valve, and sure enough, it wasn't working right, so I replaced it. The problem remains. I have not worked on it any further than that yet, but am interested in anything else anyone has to say on this phenomenon.

Faster Rat

You need to read this thread

http://forums.corvetteforum.com/c3-g...inch-test.html

Problem is likely a leak in the control side
Check valve
Wiper 3 port switch

Lemans Blue 69

I had the same problem and had a corvette shop fix it. I have know idea what the part is called but I watched him. He removed the screws that attach the louvred cowl just in front of the wiper door. There was some kind of valve on the passengers side that had vacuum lines attached to the. The plastic valve was shot. He replaced it and it has been working fine since. Can't see it without removing that cowl. Had the problem for years.

Don't know if it will solve your problem, but no harm in looking. Easy check.

Lemans

Roughrider

I looked it up and it's called a wiper door vacuum switch or a safety valve. My '69 has the same problem so now I know what to look for at Carlisle in a few days.

PUNISHER VETTE

I can tell you I have a brand new vacuum switch.(the thing under the cowl on the passenger side with 3 hoses going into it.) So i'm pretty confident that's not the problem. But just to be sure i'll double check that tomorrow and see if it's contacting just right for it to work.


I can try that pinching off the check valve and seeing what happens. I guess that way i'll know if there's a leak at least somewhere.

0Virginia Vettes

See us at J-14 they will be there

PUNISHER VETTE

I tried pinching off the check line and it failed instantly. Headlights and wiper door popped up.


So this now tells me what you think?

...Roger...

You have a leak in the control or small hose side of the system.
Try pinching the red hose going into the vacuum switch under the right wiper arm to see if that pops the wiper door only up.

PUNISHER VETTE

I guess I don't know the what consists of the control side of the system and what pinching of certain lines is actually telling me.

Roughrider

I'll look for you. Do you carry that part?

shrekviper

What? They're not supposed to do this normally to let you know the engine is running?

I've got the same problem on my 69. It's already been said, but maybe a leak on the control side. I hear some hissing sounds when I turn on the lights and/or wipers. I'll be redoing my interior (carpets, dash, stereo) and this will be a "while I'm at it".

Sometimes even new parts may have leaks. If you still can't figure it out, check each part separate from the system.

...Roger...

The control side is all the small hoses. Look at one of your vac relays,it will have 3 large hoses and 1 small,the small is the control side.

Pinching...the first pinch you did showed up a general leak in the control side. The second pinch I ask you to do will hopefully narrow down your leak to the vac switch under the wiper arm , the wiper door relay or the hoses going to both those items.
If on the second pinch the wiper door doesn't pop up then we have to back up and pinch elsewhere.

GD70

Did you also replace the vacuum filter & check valves? I read in a similar thread that these could also cause your symptoms if they are bad.
Glenn

PUNISHER VETTE

Actually I do have a new actuator relay for the engine area, kept the old one for the headlight area.

I also have installed a new hose kit so most of the hoses are brand new. I haven't gotten around to getting all of the hoses installed yet so we'll see.

Just took the distributor apart so i'll have to check that other hose when i get it back on.

PUNISHER VETTE

I still haven't figured this out yet but it's getting on my nerves.


I did notice that the door also opens during WOT
Does this tell my anything? Like something isn't working the way it should?

...Roger...

Thats usually the check valve.

PUNISHER VETTE

and the best way to check the check valve?
I'm going back through the link provided above and it seems like a lot of people have this problem yet still can't figure it out as well...

Seems like I need to pinch the line between the manifold and check valve while car is running, turn car off, wait a bit, turn car on and see if the wiper door still pops up?

PUNISHER VETTE

Okay. When i pinched the line just after the manifold and before the check valve the wiper door didn't pop up when i started it.

BUT I also see the previous owner was doing some weird things with the check valve. Has some strange tape(maybe just old scotch tape turned black) on the thing trying to hold the hoses on it.

There is the 1 intake line and 1 output line that I haven't replaced on the thing yet. The red line to the wiper switch has been replaced( the 2nd output line).

So i think i'll replace the two I haven't yet and see if that helps anything. Then if it doesn't I know the check valve itself isn't working right? Or do I already know this because of WOT or other factors?

Derrick Reynolds

Bad news to report:

Over the weekend I finally got the new wiper switch that goes under the grill. I changed it out and took her for a ride tonight. The wiper door still opens and shuts at start up. So far, I have replaced with new parts:

1. The check valve
2. The vacuum filter
3. The wiper door actuator relay
4. the wiper switch on the firewall.

Checking the check valve: The check valve is there to make sure that air flows only one way, toward the engine. To test it, if you suck on the single port side, you should be able to easily suck air. If you plug one of the two ports on the other side and suck on the unplugged port, you should not be able to suck any air. If you can't, change which side you are plugging and sucking, if still no air, your check valve is good. My old check valve failed this test, the new one passes.

My car passed the pinch test on the control side when I replaced the wiper door actuator relay.