'72 Wiper Arm Control Valve
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Le Mans Master
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From: I'd like to propose a toast... to internal combustion and wind in the face.
'72 Wiper Arm Control Valve
For quite some time I've been needing to replace my wiper arm control valve on my '72 as the spring and the button on top of the valve disintegrated leaving the wiper door unable to communicate with my wipers. The valve, http://www.volvette.com/Merchant2/me...Category_Code=
has three lines going to it that I had no problem hooking up but I do have a question about the top line (the all black line line nearest to button). The top line is a vent line that I suppose vents the air that is compressed by the plunger located inside the control valve. I would imagine that in a perfect world this line would not allow the vacuum system to leak after the car was shut off but that's exactly what happened. After hooking the valve up and verifying that it operated correctly by turning on the wipers on and then off again, I shut the engine off and began hearing a "hiss". I then narrowed the "hiss" down to the vent line on the relay valve.
My question is does everyone's valve leak like this or is it only my brand new one that I paid over $20 for. Also, it looks like this would be a constant vacuum leak affecting engine performance. Anyone got any input?
Thanks,
Mudbone64
has three lines going to it that I had no problem hooking up but I do have a question about the top line (the all black line line nearest to button). The top line is a vent line that I suppose vents the air that is compressed by the plunger located inside the control valve. I would imagine that in a perfect world this line would not allow the vacuum system to leak after the car was shut off but that's exactly what happened. After hooking the valve up and verifying that it operated correctly by turning on the wipers on and then off again, I shut the engine off and began hearing a "hiss". I then narrowed the "hiss" down to the vent line on the relay valve.
My question is does everyone's valve leak like this or is it only my brand new one that I paid over $20 for. Also, it looks like this would be a constant vacuum leak affecting engine performance. Anyone got any input?
Thanks,
Mudbone64
Safety Car
Joined: Apr 2000
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From: Wichita KS
That short black hose is in fact a vent hose. The red striped hose is a constant vacuum source and the white striped hose is the control line from the relay.
The purpose of the vacuum interlock switch is to tell the wiper door when the wiper arms are fully parked so it is safe to shut the door.
When the wiper arm is parked it depresses the button on top of the interlock switch which changes the vacuum route from the control hose to the vent hose which in turn causes the relay to change vacuum sources which changes the vacuum flow to the actuator thereby closing the wiper door.
This is probably a somewhat simplified explanation but basically how it works. DWncchs is much more knowledgeable about this than I am as is Willcox and I'm sure they will correct any mis-statements I may have made.
cc
The purpose of the vacuum interlock switch is to tell the wiper door when the wiper arms are fully parked so it is safe to shut the door.
When the wiper arm is parked it depresses the button on top of the interlock switch which changes the vacuum route from the control hose to the vent hose which in turn causes the relay to change vacuum sources which changes the vacuum flow to the actuator thereby closing the wiper door.
This is probably a somewhat simplified explanation but basically how it works. DWncchs is much more knowledgeable about this than I am as is Willcox and I'm sure they will correct any mis-statements I may have made.
cc
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From: Dayton, Ohio
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Le Mans Master
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From: I'd like to propose a toast... to internal combustion and wind in the face.
When the wiper arm is parked it depresses the button on top of the interlock switch which changes the vacuum route from the control hose to the vent hose which in turn causes the relay to change vacuum sources which changes the vacuum flow to the actuator thereby closing the wiper door. cc
Safety Car
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From: Wichita KS
cc
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Le Mans Master
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From: I'd like to propose a toast... to internal combustion and wind in the face.
First and foremost, I appreciate your participation, but I'm having trouble understanding how when the engine is in operation and supplying constant manifold vacuum, the wiper door is shut and the vent hose is "venting" vacuum engine performance won't be affected.
Safety Car
Joined: Apr 2000
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From: Wichita KS
The wiper interlock switch does not control any actuators it only sends a vacuum signal to the wiper relay to signify the wipers are parked. The entire vacuum system is closed. The air vented from the interlock switch is only for the interlock switch. Once the door is closed the interlock is no longer active and vacuum passes through the switch and is passed on to the manual override switch.
cc
Last edited by CCrane65; Aug 20, 2009 at 11:04 AM. Reason: replace "bypasses" with "passes through"
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Thread Starter
Le Mans Master
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From: I'd like to propose a toast... to internal combustion and wind in the face.
Again, correct me if I'm wrong, but are you saying that if when the engine is running, the wiper door is closed and I can detect vacuum at the open end of the vent hose that the newly purchased wiper arm control valve is leaking and isn't operating properly? Please, bear with me.
Safety Car
Joined: Apr 2000
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From: Wichita KS
Again, correct me if I'm wrong, but are you saying that if when the engine is running, the wiper door is closed and I can detect vacuum at the open end of the vent hose that the newly purchased wiper arm control valve is leaking and isn't operating properly? Please, bear with me.
I know this one. Your switch is not making full contact with the wiper arm. I had the same problem and you need to adjust the interlock switch to sit closer to the wiper arm.
cc
PS, if you push down on the wiper arm it should stop hissing. The switch isn't completely closing.
Last edited by CCrane65; Aug 20, 2009 at 11:29 AM.
Thread Starter
Le Mans Master
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From: I'd like to propose a toast... to internal combustion and wind in the face.
CC, you obviously know worlds more about these systems than I could learn in quite some time, so I'll defer to your wisdom and just have to take your word that there's no problem with wiper arm control valve. Right now my brain's just all locked up about how I could be feeling constant vacuum at the end of the vent hose while the engine is running (door up or down) and the vacuum system be deemed normal.
Thanks again,
Mudbone64
Thanks again,
Mudbone64
Thread Starter
Le Mans Master
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From: I'd like to propose a toast... to internal combustion and wind in the face.
CC,
I didn't catch your edit until after I made my last post. I'll give adjusting the relay a try tonight and thanks again for the tip.
I didn't catch your edit until after I made my last post. I'll give adjusting the relay a try tonight and thanks again for the tip.
Team Owner
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From: Crossville TN
The wiper vacuum switch should not "hisss" when you turn off the car. That line IS a vent line...but it is meant to vent when the valve transfers from passing vacuum to sealing-off vacuum. If the valve is leaking when the wiper is depressing it, then the valve is not adjusted properly. I have learned [from a prior post] that some of the new replacement switches DO NOT have elongated mounting holes in them. Thus, they cannot be adjusted properly in many cases. When the wiper is in the "parked" position, that switch needs to be raised into the wiper until that "hisss" completely disappears. The bolts should be locked down at that point and the switch will work as intended. Of course, you could figure out how to get the right wiper to close further. 
Good luck with that one! If you need more adjustment in that valve, just elongate the mounting holes [as needed] with your Dremel or a round file.
Good luck with that one! If you need more adjustment in that valve, just elongate the mounting holes [as needed] with your Dremel or a round file.
Safety Car
Joined: Apr 2000
Posts: 3,802
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From: Wichita KS
The wiper vacuum switch should not "hisss" when you turn off the car. That line IS a vent line...but it is meant to vent when the valve transfers from passing vacuum to sealing-off vacuum. If the valve is leaking when the wiper is depressing it, then the valve is not adjusted properly. I have learned [from a prior post] that some of the new replacement switches DO NOT have elongated mounting holes in them. Thus, they cannot be adjusted properly in many cases. When the wiper is in the "parked" position, that switch needs to be raised into the wiper until that "hisss" completely disappears. The bolts should be locked down at that point and the switch will work as intended. Of course, you could figure out how to get the right wiper to close further. Good luck with that one! If you need more adjustment in that valve, just elongate the mounting holes [as needed] with your Dremel or a round file.
Good luck with that one! If you need more adjustment in that valve, just elongate the mounting holes [as needed] with your Dremel or a round file.Actually, I just found an adjustment this morning that will make the wiper go down further, or at least as far as the park bracket in the middle.
The wiper transmission arms have elongated mounting holes in the center where they attach to the transmission. My wipers were hitting in the middle so I used the left transmission arm adjustment bolts to push it lower than it had been and they stopped hitting.
We are only talking about 1/4" swing in the elongated holes so you're not going to move them a lot but I am pretty sure it is enough to take care of the interlock switch problem we have been seeing.
cc
Burning Brakes
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From: Henrico VA
I believe the vacuum check valve near your master cylinder for your brakes will make you feel better. It only allows vacuum to go one way, so I think it prevents the engine from wasting vacuum.
Also, I was able to bend the metal bracket that my wiper valve sits on and that helped me adjust it perfectly. I can turn my car off in the middle of the cycle and the wipers will park causing the door to drop after them. It is truly beautiful when it works.
Also, I was able to bend the metal bracket that my wiper valve sits on and that helped me adjust it perfectly. I can turn my car off in the middle of the cycle and the wipers will park causing the door to drop after them. It is truly beautiful when it works.
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Le Mans Master
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From: I'd like to propose a toast... to internal combustion and wind in the face.
Thanks to CC and all who have posted. I was able to get the control valve moved up close enough to the wipers so that the vacuum leak was cut off.
Thanks again,
Mudbone64
Thanks again,
Mudbone64
