The wiper door control valve has three vacuum lines. One of them is called 'vacumm dump'. Is this suppose to be open? I just looked at mine, and it is plugged with a ball bearing.

Here are the three hoses entering through the firewall.


Thanks.

 

Yes, it is supposed to be open. I would guess that someone looked at the open nib of the hose coming out of the firewall and though that can't be right. I suppose it drove them crazy for a while trying to find out where it was supposed to connect to.

 

Hmmm... would this explain why my door has trouble closing? 3 of 4 times when I close it, the door does not come flush with the hood; it sticks up about 3/8". Sometimes I can push it down. I assumed it was the linkage binding.

 

Mine has been rebuilt by the previous owner and works perfectly. I have been caught in light rain twice with no problems.

I did put Rain X on the windshield rather heavy to reduce the load and hope I never need to turn on the wipers. :)

 

Yup. That's merely a vent tube and should be open. A bb in the end? Interesting. I use golf tees. :)

It just vents under the hood rather than under the wiper door so it doesn't ever suck in water (or so I'm guessing).

Dave

 

That mysterious vent tube is supposed to be open as it's the suction source for air into the diaphram of the vacuum controll relay, that relay is spring loaded to return to the door open position when controll vacuum is released from the relay....that happens when the wipers go all the way down to park, hopefully clearing the door enough to allow it to close all the way...if it doesn't make sure first off that the wipers are seated all the way,....pull the main vacuum line from the controll relay center position and temporarily reroute it to either side of the vacuum motor canister...leaving other side open....start engine to get vacuum source running...and check the actuator motor for operation...door should spring open and closed immediately, and completely....

actually i'ts a fairly simple system, just takes getting used to....

it's that edjemakation about it that's the bitch....

GENE :D :D :eek: :eek: :cool:

 

Yup. It took me a little while to figure out what exactly everything was doingt, but then I thought "That's brilliantly simple!" Maybe not 100% reliable, but simple.

 

And here I thought that cut off tube was something Bubba did. Now I can quit letting the look of that depress me. :lol:

Before I went to Carlisle, I did the RainX. I highly recommend it.

My door works fine, but like you, the wipers don't park deep enough on their own and the door is kept from parking completely flush. I was hoping mrvette was going to explain how to adjust the depth of the wiper park. If he did, I'm to stupid to see the explanation.

Please tell us what happens after you remove the beebee.

:cheers:

 

At the risk of offering an obvious solution to wipers that don't park completely, I will ask the question. For those 68-72 owners with wiper arm problems, are you aware that there is an arm adjustment procedure in the Assembly Instruction Manual? Fairly simple, five minute job. This ensures that the wiper blades park properly and the door shuts without hitting anything. The AIM is a must have item and even a good read on a dull evening. There are lots of adjustments procedures given there.
Gary

 

I have a GM Corvette Shop Manual. Is this the same thing as the AIM?

:cheers:

 

GM shop manuals are just repair oriented....for our sharks, well mine is the car manual covering all '72 chebbys....and an overhaul manual also, covering all the major sub assys....

the adjustment of that vacuum switch is a bit complex in that it only changes positions when the wipers are operating, and then again when they are parked...ALL THE WAY DOWN AND HOME....LO AS THEY CAN GO....

of not the door will close on top[ of them.....and break something....
easy to do....

what happens is the system is a 'suck down system'.....so if the CONTROL side of the vacuum switch...the single lone small hose.....has NO suck on it, the spring loaded vacuum relay tells the door to open....
when it opens, the wiper is then energised via that switch and hook arangnement next to the engine distributor....
so that's if the door is open....wipers are then actuated, door has to be open all the way.....
NOW if someone turns off the wipers with them in the wipe position, and the door would be permitted to close....well then it would go crunch....
SO regardless of what signal comes from the wiper switch via the expensive non reporduced wiper vacuum relay on these sharks...the one behing the tach.... regardless if that vacuum source is live or not....
the switch on the wipers passes vacuum to the relay on the fender liner....
keeping the door open, UNTIL the wipers return down to park position...

IF like me, you have a delayed wiper function (I built my own)....it's easy, my vacuum switch failed, and so I may someday get around to making an electrical interface/switch hooked up to controll the main switched valve...the electrically operated vacuum switch they mounted behind the tach....I moved it to under the hood...that way I can see it, and work with it if necessary.....that way I don't have to tear the entire car apart again to fix something simple.....I do all that type of changes automatically to any car I own....

GENE :D :D :D :eek: :cool:

 

OK, to see if the vacuum actuated wiper safety switch if actually bad....
you need pull the line to the controll relay, engine running, AND THE TWO LINES TO THE VACUUM CANISTER OR THE MAIN FEED LINE TO THE VACUUM RELAY....plug the line (s).... see the door open up....and then take vacuum gauge to that controll hose...if there is full engine vacuum there, fine....you need pull the wipers up to operating, then turn them off with the controll switch under the steering column....
now they are up in the windshield somewhere....reach down and see if that vacuum switch on the pass side blade base down under....pushwith screwdriver and change positions on that switch....it should be able to bleed off the vacuum of the main controll vacuum relay diaphram....and allow the door to close.....but we have a gauge on that so we watch for the switch to drop ALL the vacuum....if it wont' drop all the vacuum....
the door may close prematurely...as the switch is passing vacuum even a little bit due to internal leakage....
ME with intermitant wipers....I wait untill they are down all the way...then close the door/system down....that way I don't really need the switch....
but IF I goof and shut down system with wipers in up postiion....well I"m screwed.....

GENE

 

OK, to see if the vacuum actuated wiper safety switch if actually bad....
you need pull the line to the controll relay, engine running, AND THE TWO LINES TO THE VACUUM CANISTER OR THE MAIN FEED LINE TO THE VACUUM RELAY....plug the line (s).... see the door open up....and then take vacuum gauge to that controll hose...if there is full engine vacuum there, fine....you need pull the wipers up to operating, then turn them off with the controll switch under the steering column....
now they are up in the windshield somewhere....reach down and see if that vacuum switch on the pass side blade base down under....pushwith screwdriver and change positions on that switch....it should be able to bleed off the vacuum of the main controll vacuum relay diaphram....and allow the door to close.....but we have a gauge on that so we watch for the switch to drop ALL the vacuum....if it wont' drop all the vacuum....
the door may close prematurely...as the switch is passing vacuum even a little bit due to internal leakage....
ME with intermitant wipers....I wait untill they are down all the way...then close the door/system down....that way I don't really need the switch....
but IF I goof and shut down system with wipers in up postiion....well I"m screwed.....

GENE :mad :mad :confused: :D :D :eek: :cool:

 

Different animals. The AIM tells how to adjust the wiper arms as they are being installed. The Shop Manual tells how to repair the wiper motor, etc.
Gary

 

Gary,

It looks like the AIM comes in a 3 ring binder. I'll get one. Can I live w/o the index?

Thanks for the help. We live about 15-20 miles apart and both of us have 72 coupes. Do you ever go to any shows or cruises?

Jay :cheers: