Wiper Door Question
Thread Starter
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
Wiper Door Question
The wiper door on my 71 opens and then closes on start up. Some old threads suggest the cause is a vacuum leak at the check valve. My check valve is good.
I think all other vacuum hoses are correct per Wilcoxx diagram.
Any other ideas as to what is causing this?
I think all other vacuum hoses are correct per Wilcoxx diagram.
Any other ideas as to what is causing this?
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Leaks and low pressure. It can be anywhere, but is usually at the actuator boot, or the vacuum valve, assuming that the check valve is good.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
The wiper door is the first and easiest thing to work when the engine starts. If the vac system is empty or low the door will pop up and go down before the system has a chance to equalize.
"ANY ITEM" in your system could be leaking very very slightly causing the system vac to drop low enough for the wiper door relay to relax into the "up" position. If your only issue is the door popping up and then going down I have found by restricting the yellow hose ( you can do all 3 hoses if you want) at the wiper door relay this stops the annoying up and down action of the door. It also slows the action of the door to stop that guillotine action.
(Why restrict now if the factory didn't ? I think there might be a difference in the relay springs of the repopped relays and also I think the door action is looser than when the car was new. )
"ANY ITEM" in your system could be leaking very very slightly causing the system vac to drop low enough for the wiper door relay to relax into the "up" position. If your only issue is the door popping up and then going down I have found by restricting the yellow hose ( you can do all 3 hoses if you want) at the wiper door relay this stops the annoying up and down action of the door. It also slows the action of the door to stop that guillotine action.
(Why restrict now if the factory didn't ? I think there might be a difference in the relay springs of the repopped relays and also I think the door action is looser than when the car was new. )
Advanced
Joined: Apr 2002
Posts: 68
Likes: 0
From: Baton Rouge LA
Mine won't open unless I nudge the plunger with my fingers, then it opens just fine. Needs a nudge to close, as well, before the vacuum takes over. I'm assuming that means the leak is in the actuator boot, because there's enough vacuum to pull the skin off your hand off from the front access hole, when the plug's out. :-) Lights come up and down, just fine.
Team Owner
Joined: Sep 2006
Posts: 31,230
Likes: 4,324
From: Westminster Maryland
Hi Roger,
I think you make an interesting point.
I was taught that the 'supply' (actuator) hoses were large and the 'control' (relay) hoses were small so that at start-up the control relays would have full vacuum (and send their 'close' signal) BEFORE the supply to the actuators would have enough vacuum to open the lights and wiper door. This was in the design to keep the doors closed even if the 'control' vacuum had leaked off while the car was sitting.
If I might ask...what do you use to restrict the yellow supply hose and where do you put it?
Regards,
Alan
I think you make an interesting point.
I was taught that the 'supply' (actuator) hoses were large and the 'control' (relay) hoses were small so that at start-up the control relays would have full vacuum (and send their 'close' signal) BEFORE the supply to the actuators would have enough vacuum to open the lights and wiper door. This was in the design to keep the doors closed even if the 'control' vacuum had leaked off while the car was sitting.
If I might ask...what do you use to restrict the yellow supply hose and where do you put it?
Regards,
Alan
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Hi Alan,
I'm not sure about that way of thinking and if that was part of the design.
IMO more vacuum volume is going to flow through the larger less restricted hose.
With the smaller hose the large source of engine vacuum is going to be restricted by the small hose and charge through the larger unrestricted hose to the actuator and BOOM up it goes before the vacuum can get through the small hose and move the valve in the relay from the down position to the up position.
Another thing to consider is when the vacuum builds in the system 0-1-3-4 and so on its going to try to build through out the system the same large or small hose.
The wiper door actuator will move with about 2" of vacuum.
The control part of the valve takes about 4" of vacuum to move the valve from the open position to the close position.
Alan for a restrictor I used a piece of plastic with a 3/32 hole that I slide inside the yellow hose. (I started out restricting the green up hose but liked the softer movement so well that I moved it to the yellow so it would effect open and close.)
I'm not sure about that way of thinking and if that was part of the design.
IMO more vacuum volume is going to flow through the larger less restricted hose.
With the smaller hose the large source of engine vacuum is going to be restricted by the small hose and charge through the larger unrestricted hose to the actuator and BOOM up it goes before the vacuum can get through the small hose and move the valve in the relay from the down position to the up position.
Another thing to consider is when the vacuum builds in the system 0-1-3-4 and so on its going to try to build through out the system the same large or small hose.
The wiper door actuator will move with about 2" of vacuum.
The control part of the valve takes about 4" of vacuum to move the valve from the open position to the close position.
Alan for a restrictor I used a piece of plastic with a 3/32 hole that I slide inside the yellow hose. (I started out restricting the green up hose but liked the softer movement so well that I moved it to the yellow so it would effect open and close.)
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Another possibility is that the 'vacuum transfer tube' [which runs across the length of the firewall to the vacuum safety switch under the right wiper] is clogged up and nearly closed off. It has a "V" shape bent into it, where it goes under the wiper motor, which can collect moisture and form corrosion. It is very difficult to clean out without removing it from the firewall {which is a real PITA}. Removing the hoses at each end and blowing it out with compressed air is your best bet...if that is your problem. I have yet to come up with a flexible item for pushing through it to clean it. Something strong enough to clear it won't make the bend at the bottom; something light enough to make the turn won't go all the way through???? (Any suggestions for this would be appreciated.)
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Another possibility is that the 'vacuum transfer tube' [which runs across the length of the firewall to the vacuum safety switch under the right wiper] is clogged up and nearly closed off. It has a "V" shape bent into it, where it goes under the wiper motor, which can collect moisture and form corrosion. It is very difficult to clean out without removing it from the firewall {which is a real PITA}. Removing the hoses at each end and blowing it out with compressed air is your best bet...if that is your problem. I have yet to come up with a flexible item for pushing through it to clean it. Something strong enough to clear it won't make the bend at the bottom; something light enough to make the turn won't go all the way through???? (Any suggestions for this would be appreciated.)
Team Owner
Joined: Sep 2006
Posts: 31,230
Likes: 4,324
From: Westminster Maryland
Hi Roger,
It's an intermittent problem which has made it a BEAR to locate.
I was intrigued with your 'band-aid fix' which would allow me to put it further down on my list.
Regards,
Alan
It's an intermittent problem which has made it a BEAR to locate.
I was intrigued with your 'band-aid fix' which would allow me to put it further down on my list.
Regards,
Alan
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Alan I'm not sure you will actually find the exact cause because were now dealing with apples and oranges. I doubt very seriously if you will ever find flow stats on the original relays and vacuum components. I also doubt if there is a way to measure the resistance of the wiper door in relation to the actuator. I do know from what I remember years ago most doors open and close much faster than they used to. I think there are too many new and changed components to compare.
We all know that the system does in time leak down,no doubt about that, so it becomes all about the way the system recharges itself. I believe its a balance thing.
Maybe the vacuum flow through the new check valves has something to do with it,the originals were pretty restrictive.
We all know that the system does in time leak down,no doubt about that, so it becomes all about the way the system recharges itself. I believe its a balance thing.
Maybe the vacuum flow through the new check valves has something to do with it,the originals were pretty restrictive.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
First off, on my '72 that vac cannister under the driver's fender had stress cracks in it from all the age....permanent that could not be fixed, and with no replacements available 15 years ago, I ditched it....
too long ago now to recall just what affect that had on the headlights, but they worked 'OK" more or less, for a vacuum operated thing anyway...I used ONE vac relay up front for them....
then the wiper door, doing the popup trick, I found to cut the control relay apart, and cut some loops outta the actuation/control spring, weakening it greatly...then reseal and it worked fine then....
I went through all the vac 'diodes' and other crazy parts, and found that spring thing was the final fix....
but not really, as I now have intermittant wipers with electrical operated door on a linear actuator.....
hardly nuttin is vac operated in that car any more.....
too long ago now to recall just what affect that had on the headlights, but they worked 'OK" more or less, for a vacuum operated thing anyway...I used ONE vac relay up front for them....
then the wiper door, doing the popup trick, I found to cut the control relay apart, and cut some loops outta the actuation/control spring, weakening it greatly...then reseal and it worked fine then....
I went through all the vac 'diodes' and other crazy parts, and found that spring thing was the final fix....
but not really, as I now have intermittant wipers with electrical operated door on a linear actuator.....
hardly nuttin is vac operated in that car any more.....
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Try replacing 1 of the large hoses coming from the relay to the actuator with a small hose. I guarantee you the small hose will slow the actuator down.
Burning Brakes
Joined: Mar 2006
Posts: 915
Likes: 2
From: Lima, OH -- 69 L71 427/435hp
I was following another thread about this, may be helpful.
http://forums.corvetteforum.com/c3-t...-start-up.html
I was considering troubleshooting mine, however, since I 'try' not to get caught in the rain I never use the wipers, so I kinda like that it opens/closes a little each time as it helps keep all the joints moving and prevents them from binding/siezing up...I do the same with the headlights but at least they go up and down when I want them too.
http://forums.corvetteforum.com/c3-t...-start-up.html
I was considering troubleshooting mine, however, since I 'try' not to get caught in the rain I never use the wipers, so I kinda like that it opens/closes a little each time as it helps keep all the joints moving and prevents them from binding/siezing up...I do the same with the headlights but at least they go up and down when I want them too.
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Ha ha, that was my thread.
I watched that video on YouTube about the Mako Experimental car and noticed that all of the vacuum operated things moved slowly and deliberately.
cc
I watched that video on YouTube about the Mako Experimental car and noticed that all of the vacuum operated things moved slowly and deliberately.
cc
Last edited by CCrane65; Dec 17, 2009 at 09:57 PM.