pyro454

Hi guys,
I purchased a 70 vette and have been slowly nursing it back to health. I replaced all the vacuum hoses, filter and check valve and the wiper arm control valve. I now have a wiper door that opens and wipers that come on (most of the time).

Is it normal for the vacuum system to "decompress" after about a minute of the car being off? The lights stay down but the wiper door was coming up about an inch. I lengthened the wiper door actuator arm (by unscrewing the bolt) and now the door is a little low but stays closed after I hear a click and air escaping from the valves..

Or do I have a vacuum leak?

Any input would be appreciated!

Noob

DZRick

I believe you have a leak.

Rudy's Stingray

I have the exact same problem with my 70'.
Tonight I opened the hood to "listen" for an air leak and sure enough
I heard it. It's either at the 3 way valve or the rubber hose coming off of
the intake to it.

Joe

pyro454

Well, I ordered a new vacuum actuator valve(4 ports) the other day and will replace the old wiper one and see if that helps. I can't really hear air leaking from anywhere.

Joe, when you say 3 way valve, do you mean the one under the passenger wiper? That is brand new along with the hoses and I have adjusted it so that when the wipers are down, it is definitely closed tightly.

In your 70 vette, is there a screw in the vent hose in the "safety control valve" under the wiper? It was in mine and I saw one other pic online. I took it out as all the vacuum kits guides online do not have this.

srs244

i'd bet on it. there shouldn't be any hissing sound that you can hear with the engine running or not. you might want to double check the vacuum reserve can. many of the older C3 models had nothing more than a reasonable facsimile of a #10 fruit can for the reserve tank and they had a tendency to rust out easily. if the tank is ok, check to see if you can hear where the hiss is coming from. the switch directly under your steering column is designed to manually open the system (to change the blades or to wash the headlamps) without running the engine. it gets it's "power" from the reserve tank. if there is a leak, there will be no reserve (obviously).

pyro454

So I got the vacuum actuator valve relay and replaced the wiper one near the firewall. It did not help so I then moved it up front to replace the one I heard a "click" coming out of after the car was off. Problem solved.

Wiper Door on my 70 C3 goes up and down nicely now! (I just need to find out why the wipers won't come on now!!)

Alan 71

Hi p,
Have you checked the limit switch that's on the firewall and operated by the wiper mechanism. It's function is to NOT let the wipers start until the door is fully open.
Here's a picture of the switch.
Do you have a headlight/wiper trouble shooting guide?
Regards,
Alan

pyro454

I have done a very basic check and reconnected the wires after cleaning the connectors. Would it work to hook a voltmeter up to each side? What would be the next step in troubleshooting the switch? I do not have the headlight/wiper guide.. probably time to get one? lol

(oh and if that's you engine compartment, it is imaculate!)

Alan 71

Hi p,
For the switch... the circuit is open when the button isn't pushed, and closed when the button is depressed.
Regards,
Alan

pyro454

Well, I finally had a chance to remove the switch and test it with an Ohm meter. Works perfectly. I also bypassed the safety switch with a wire and then turned on the wiper switch and I can hear a click sound but have no wiper action... is a new wiper motor the next step?

0Willcox Corvette

Nope.. testing is next...

1 sec.. I'll post you some links.

0Willcox Corvette

Check the over-ride switch under the dash before you do anything, its right between the two vacuum switches under the column.

Then: Go here and click on supporting document.

Corvette Windshield Wiper Motor Wire Schematic 69-72 with test
http://willcoxcorvette.com/repairand...elp.php?hID=95

Next, go watch the bench testing video....

Here is a picture of the three way valve or "Check" Valve.



Video thread is here.. http://forums.corvetteforum.com/c3-g...post1578797422

7T1vette

If I'm not mistaken, the wiper interlock valve/switch does vent vacuum when the engine is shut down. If the system is not 'leak-free', the wiper door might go up a bit after a few seconds due to vacuum in the system not being retained as it should. But, otherwise, the vacuum items operate as they should. This is just one of the symptoms of a system with normal wear in seals/valves.

mark6669

check the relay under shifter plate in front of ash tray

rafalc

Hey, about that screw blocking one of the vent hoses. Take a look at this thread (post #95 pictures)...is it blocking the same vent? This is what I found in my '70, I took the screw out but behavior has not changed.... door opens and closes fine, I just have to do some testing and get the wipers to work.

http://forums.corvetteforum.com/c3-g...trieval-5.html