Just got my 70 Corvette back from the Body shop. Everything looks perfect except the windshield wiper access door pops straight up after the engine is started. Being the original owner I remeber that this door is controlled by vacuum. Since the Body Shop took the car entirely apart and then put it back together I am sure that one of these vacuum lines has been criss crossed. Any recommendations or diagrams would be greatly appreciated. Thanks, Chuck.
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Re: 70 Windshield Wiper Access Door
The assembly manual and AIM would be of great help to you. -
Re: 70 Windshield Wiper Access Door
Chuck I have a 70 but my vacuum hoses are still factory correct. Try reversing the two vacuum hoses that connect to your vacuum canister. Under your cowl vent grille there is also another valve that has multiple vacuum hoses. Dr. Rebuild's parts catalog has information on the vacuum hose routing.Comment
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Re: 70 Windshield Wiper Access Door
Another good source of information is the wiring and vacuum schmetic diagrams that are available from Olson Engineering. Don Olson can be contacted thru the profiles on this board. 1at class laminated, colored drawings. Large fer the old eyes too.Dick WhittingtonComment
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Re: 70 Windshield Wiper Access Door
Have you check to see if the wiper door override switch isn't engaged?Comment
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Re: 70 Windshield Wiper Access Door
If it pops up then re-seats on its own, you're fighting another type of problem...race condition.
When you first start the engine and pull vac, there are two paths (servo and control) that begin to 'see' vac at the same time. The servo side of the system (vac that actually does work opening and closing things) is 'buffered' by the vac storage reservoir. It takes a while to fill the vac can before there's sufficient vac available to do significant work.
The control side of the system (vac that tells the various relays when to actuate and open/close things) is unbuffered and vac lines are typically of smaller diameter to 'bias' the system to avoid a 'race condition'.
As the two sides of the system come up to pressure, you want the control side to win the 'race' and come up first. If it doesn't, then the various relay's will 'fire' in whatever state they were when the system last went down and lost pressure. That creates a transient condition where various components 'wink' or 'dance' for a period of time until the entire system is equally pressurized.
Also, the servo side of the system has parallel paths. Vac that runs the wiper door also runs the RH headlight. So, it's possible for leak(s) in another circuit area to affect the wiper door...
Typical causes for improper bias and erratic operation of various vac controlled items during startup/shut-down include:
(1) Hoses mis-routed
(2) Hoses disconnected
(3) Leaking hoses
(4) Leaking vac relays
(5) Leaking vac actuators
(6) Faulty vac check valve
(7) Clogged/plugged vac in-line filter
Item seven is one that's frequently overlooked. This filter was intended to be periodically replaced (once a year interval under normal driving conditions) and many cars are out there running around with either their factory original filter or a VERY OLD service replacement installed...Comment
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Re: 70 Windshield Wiper Access Door
Scott,
Good point. I never even thought of the Assembly Manual but will definitely open it up tonight and check it out.
Thanks,
ChuckComment
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Re: 70 Windshield Wiper Access Door
Chuck, you might want to wait until you have a clear mind and focused eyes. That manual ain't for light reading. I traced and tracked virtually every vacuum line on my '70 using the assembly manual, Dr. Rebuild's vacuum hose chart, vacuum gauges, hose clamps, telescopic mirrors, needle nose pliers.....you name it. Does everything work flawlessly? No. Do I still love the car? Yes!Comment
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Re: 70 Windshield Wiper Access Door
Jim,
I will give that a try tomorrow morning. Does Dr. Rebuild's have a website?
Thanks,
ChuckComment
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Re: 70 Windshield Wiper Access Door
Dick,
Large, colored diagrams. That works for me. :-)
Thanks,
ChuckComment
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Yes, do a Google search... *NM*
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