Duntov

My 1970 coupe with AC has an issue where the wiper door doesn't close.

A little history on the car. The car has been sitting for over 20 years in a climate controlled garage with the engine out. I replaced many of the AC parts, and all connections were checked in the AC system, as it was reinstalled. The original engine was installed just before Christmas, and spent the period till now hooking things up, breaking in the engine, etc. I know the cam is not stock, but do not know the cam specs.

With the engine running, the headlights function slowly. This may be due to low engine vacuum, bad seal in the canister, etc. The wiper door can be closed manually with vacuum, and the canister will hold vacuum. Upon starting the car, the door will open again.

The override switch for headlights work, and hard to tell since wiper door is open on the other. I can hear something behind the dash which maybe a vacuum leak. The valve on the firewall by the master cylinder seems to work in static testing.

I am thinking the solenoid on the back of the tach is the issue. Does this sound reasonable?

Being its an AC car, getting to it looks like a PITA. Is there any suggestions on ways to get at this without killing my back.

Dave J

DO NOT try to remove the solenoid if you have not tested it, and only think it might be the problem. Especially if you have AC.

Simple test would be; Remove the vacuum hose from the port closest to the pull **** on the wiper door override switch. connect a vacuum gauge to the open vacuum hose you just removed. Observe the vacuum reading with the wiper switch both on and off with the engine running. If you get a different reading, the solenoid is good.

Easily 90% of the solenoid issues I have seen is the vacuum hose has simply come off the tapered port from the 90 degree end of the solenoid. This is the next test, and it can be done with a simple small mirror. Even a leaking solenoid will still operate most of the time.

0Willcox Corvette

Dave is right, the solenoid when energized blocks vacuum on hose H in the diagram below. When your turn on the wipers the solenoid gets energized so test the solenoid before you take it out of the car.

Willcox

Duntov

So disconnect at the override and check vacuum, with switch on and off? If different reading it's working? Sorry if being dense, just trying to make sure testing best way possible to find the fault.

0Willcox Corvette

Yes... with the wipers off you should have vacuum on the blue hose, when you turn on the wipers the vacuum should fall off that hose.

Willcox

Duntov

Found that at some point in the cars life the vacuum switch in the wiper door area was MIA, the hoses were plugged with sticks. I had a new switch put it in. The wiper door still opens at start. With the engine running I get some vacuum at the override switch, there is a white hose. It goes away when the wiper switch is moved from off to on.

I am not sure how much vacuum the car is generating due to unknown cam, and not getting vacuum gaugeon it either. Also not sure of the condition of the seals of the headlight and vacuum canisters. I checked the override switch and it holds vacuum.

Duntov

I'm thinking it may be the canister by the master cylinder. The top port holds vacuum, but not sure how to test if the other functions operate as intended.

Dave J

Help us help you out here. What are you using and how are you testing the vacuum in the components you refer to?

Duntov

In most cases a handheld vacuum pump, MityVac, but for the vacuum at the override hoses was using engine vacuum.

Dave J

OK, now we have something to work with. Your Mityvac has a vacuum gauge built into it that will indicate the vacuum reading simply by attaching it to a vacuum hose. You can check your engine vacuum this way.

Most of the issues I have encountered with the "winking" wiper door have to do with an imbalance in the small hose (control) and the large hoses (actuating) circuits. Simply, the control circuit is leaking vacuum (actually allowing atmosphere) while the actuating circuit is being fully charged. In this scenario, the wiper door will rise till the control circuit "catches up". Your job is to diagnose which component(s) are causing it to happen.

Most of the time, the wiper door safety valve is the culprit. This is the valve beneath the passenger wiper arm. You can also bypass this valve to check its function by simply connecting the two hoses together that connect to it. The hoses should be colored red & white.

If you have the wiper door raising and lowering, I would not worry about the actuating hoses at the relay (the canister by the master cylinder). It is working well enough. Focus on the diagnosis in the control side.

Duntov

The safety valve is now new, since previous owner put twigs in the hoses to seal them off.

Currently the door opens at engine start, regardless of wiper switch position. From the diagram that Willcox posted the "green" line is working, but the "red" one isn't. Not sure how to make the red one actuates the door to verify things are operating correctly.

Dave J

That doesn't necessarily mean it is a good valve.

Vacuum must be present at the "F" position from the small white hose from the safety valve leading to the relay for the door to stay closed. You can simulate this by connecting a short hose to the small port on top of the relay, and connecting your Mityvac to it. You can then pump up that control vacuum line, mimicking the control vacuum. When you start the car, the door should stay closed. Try it.

Duntov

Found the issue. The red hose from the switch in the wiper valley has a hole in it. Put some air through it after not being able to get vacuum from either hose at override to the valley, and felt the air coming out under the column. Put some air from wiper valley red hose tomin the car. Not sure if they are taped together in the car and can use the old hose to pull a new one.