72 wiper door issues at wits end

[Stephen B.]

Need an issue fixed which is most likely simple. What will makes the wiper open after starting the car? I've replaced most of the parts required after sitting for over 15 years of sitting. To close the wiper door I have to pull the vac hose of the actuator or just let the car sit. Thanks for any help here.

[Patrick H.]

Re: 72 wiper door issues at wits end

Odds are there is a vacuum leak somewhere in the system.
Each part needs to be tested individually. In addition, one of the new parts may already be leaking or not working up to specs. That is not uncommon.

Not much needs to be replaced after 15 years of sitting, so you may have removed a good old part and installed a bad new part. That happens more than one would think.

Was the problem happening before you replaced parts?
What did you replace, and what did you not replace?

[Michael C.]

Re: 72 wiper door issues at wits end

System is losing vacuum when sitting. You can borrow, with a deposit, a vacuum pump at most of the auto parts stores and connect it to the Vac hose leading to the check valve. Run it for a bit and shut it off. You should be able listen for to isolate the leaks this way. No engine noise. I was able to isolate 3 Vac leaks in my system this way.

[Terry M.]

Re: 72 wiper door issues at wits end

Need an issue fixed which is most likely simple. What will makes the wiper open after starting the car? I've replaced most of the parts required after sitting for over 15 years of sitting. To close the wiper door I have to pull the vac hose of the actuator or just let the car sit. Thanks for any help here.

I hate to type all this again, but I am too sick to do much else.

There are a couple of what I am told are good reference sources at Wilcox Chevrolet and Dr Rebuild has a vacuum troubleshooting manual, but I have availed myself of neither so my recommendations are third hand and may not be current. Cliff Notes:

A fundamental understanding of the operation of the vacuum system is required to trouble shoot it.

The system consists of two parts -- the control circuit (small hoses) and power circuit (larger hoses). There is also a vacuum reservoir, but that is not enough to be a separate circuit. I mention it so it is not ignored.

The system is deigned for the control circuit to have a smaller volume (remember smaller hoses) than the power circuit. Thus when the engine is started after a long rest vacuum will suck the control circuit to vacuum before the power (larger volume). If there is a leak in the control circuit things like winking headlights and up and down wiper door will take place. If the leak is large enough in the control circuit for that part it may operate and stay in that position.

Now that you understand the basics you should have a place to start.

Patric has also offered some hints which I will repeat. DO NOT ASSuME NEW PARTS ARE GOOD
Unless you bought your parts from Bob Demmil, chanches are good they are dead on arrival.

[Terry M.]

Re: 72 wiper door issues at wits end

System is losing vacuum when sitting. You can borrow, with a deposit, a vacuum pump at most of the auto parts stores and connect it to the Vac hose leading to the check valve. Run it for a bit and shut it off. You should be able listen for to isolate the leaks this way. No engine noise. I was able to isolate 3 Vac leaks in my system this way.

You make another good point which I failed to mention: DO NOT ASSuME THERE IS ONLY ONE LEAK Leaks are like mice. They travel together. Get used to it and keep searching.

[Patrick H.]

Re: 72 wiper door issues at wits end

The new check valves that are located "near" the intake manifold are sometimes useful, sometimes not. I buy good originals when I can. There seems to be more than 1 manufacturer of this part in reproduction land.

The new valves that fit in the windshield wiper trough have a 90% failure rate IF you buy the foreign-made version. It has to do with where they put the seam for the mold. There is a gentleman on CF who sells US made ones, and they are far better. Some vendors also sell his valves.

The relays in the nose and right fender can also leak. Bob Demmel can rebuild them, or new ones seem to be OK.

[Stephen B.]

Re: 72 wiper door issues at wits end

Thanks to all for the information. The problem will be fixed.

[James B.]

Re: 72 wiper door issues at wits end

Keep us posted on your findings. Thanks.