Everything works fine except when you start the car, the door goes up and then comes back down. I figured the check valve, but that's ok. The switch and under dash override seem to work ok. Other ideas? Could the park switch be the problem?
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Re: 69 Wiper Door BUGS!
Wayne,
My 69 has been doing that for 27 years! It's a ritual I look for everytime I start the car. I have a leak in one of the hoses that runs behind the wiper motor, and can hear the leak down when I shut off the car. I would imagine using a vacuum pump would work to isolate the problem.
Don Smith #28087 -
Re: 69 Wiper Door BUGS!
This is NOT normal and indicates your vac system is leaking. There have been many threads on such in the past (check the archieves) and there are books from most of the catalog houses on troubleshooting the Shark vac system. Reading and understanding is KEY to finding and fixing. Do NOT presume there's only ONE leak source! Once you start to troubleshoot the system, go all the way and find/kill all the bugs....
Here's a thumbnail. The vac system is divided into two pathways: (1) control (vac signals that instruct vac motors/switches to open/close), and (2) servo (vac paths that do the actual work of opening/closing this/that). Hose size and length were intentionally controlled by designers to 'bias' the system properly. On initial engine start-up and development of vacuum, insure the control side of the system comes up FIRST to thwart random 'fluttering' of vac actuated components based on what state they 'relaxed' to on the prior power down cycle.
The dancing wiper door and winking headlight syndrome are evidence there's problem(s) with the relationship of the control vs. servo side of the system resulting in a 'race' condition. This can be as simple as worn/plugged check valve (remove and test by blowing/sucking) or a worn/plugged in-line filter (remove and sight through it to a light source; you ought to see clean white cotton). The later was intended to be replaced once/twice a year under normal driving conditions, but few ever bother to replace. Or, you can have one or more leak points in the system (common places are HL actuator front seals and wiper door actuator + relay plus worn frayed rubber atop various connecting nipples). Typically, I find a combination of ALL the above....
An excellent method for troubleshooting the system is to get a LONG vac hose. Park your passenger car/truck out in the driveway, tee off it's engine vac, run the hose into your garage, close the door and use the second vehicle as a 'noiseless' remote vac source for your Corvette instead of running the target vehicle's engine....Comment
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Re: 69 Wiper Door BUGS!
Wayne -
I spent many hours trying to troubleshoot this same contiion on my '69. Everything continued to point to a vacuum leak in the control circuit because as soon as the system "settled" the door would immediately close.
My situation was unique in the fact that the entire system was new except one piece - the electronic vacuum switch. This is the switch that is mounted behind the tach that takes the electronic signal from the wiper switch and triggers the vacuum control circuit to open and close the door. I had manually tested the switch before the dash was reinstalled and everything seemed to work fine.
Since there were not any vacuum leaks and all other components tested okay, this was my last resort. I removed the switch and drilled open the rivits to release the housing. The switch is very simple in that a plunger travels back and forth in the cylinder based on electrical current. The plunger allows vacuum to follow one of two circuits. The problem with my switch was that a very small amount of grease was on one end of the plunger. By cleaning the plunger and reassembling the switch, the problem was eliminated.
It seems that the grease was simply slowing the control circuit to the point that the servo circuit "beat" the control circuit when the car was started. Unfortuneatly I do not think this part is available unless you can find a NOS version. I hope this helps.Comment
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Re: 69 Wiper Door BUGS!
There is no headlight problem on this car, only the wiper door. As stated previously, the check valve is good. I've fixed a number of possible vacuum leaks. There could be more. I will check the filter as I have not done that.Comment
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Re: 69 Wiper Door BUGS!
Wayne -
The switch that I am refering to controls the wiper door, not the headlights. It is mounted behind the tach. It is a small cylinder with two electrical contacts and two vacuum lines. Good luck.Comment
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