I am looking for some tricks and advice on troubleshooting the vacuum system on my 72 C3. I don't think this is normal, but ever since I bought the car when I would start the motor the wiper door would lift then close. I suspected something funny was going on, but didn't start the diagnosis because the door would always retract. Last week I started the car up and the door opened as usual, but this time it didn't go back down. I have traced all exposed tubing for signs of dry rot or a loose connection, but everything looked good. I think a may hear a small vacuum leak coming from under the steering column where the switch controls to operate the lights and wiper door are located, but I can't pinpoint it over the sound of the engine. Do any of the vacuum experts here have some advice on how to identify the failure in my vacuum system? I will be happy to provide any additional info needed. Thanks!

 

There are two types of C3 owners in the world, those who own a Mityvac and those who will own a Mityvac. Sounds like you are about to become one of the first type.

In all seriousness a Mityvac and a couple of golf tees to plug vaccum lines makes finding leaks pretty simple.

 

I like Iceaxe's answer - humorous and true at the same time.

I'm troubleshooting some wiper door issues too.

I ordered this from Amazon yesterday (sorry if I'm violating forum rules since Amazon isn't a supporting vendor?):


In addition, you may find the following youtube video helpful:


On top of that, there are some really helpful forum members that I'm sure will chime in, include some pics, etc. They've been very helpful to me - a 'few quirks' on our C3s and knowledgeable forum members really help.

Good luck!

 

Thanks for the feedback guys. I will soon be a C3 owner who owns a Mityvac. Thanks for posting the video Hopper, hopefully it will be a huge help. I will let you guys know what it was.

 

Hi e,
It may be a help to understand how the headlight and wiper door systems work.

I wrote this for another post a couple of weeks ago.
A wiper door that opens on start-up but then closes is one of the common problems for both the headlight doors and wiper doors.
Perhaps this will help you get started in tracking down the cause of your problem.

"You describe what some people have called a 'dancing' wiper door.

The vacuum systems for the headlights and wiper door have 2 'sides'.

The 'servo' side is the part of the system that actually moves the doors.
It consists of the actuators, the large hoses, and the storage tank.
The 'control' side of the system determines which side of the actuator ('open'...green hose or 'close'…red hose) receives the vacuum and consists of the switch (for headlights), relays, safety switch and solenoid (for wiper door), and small hoses.

The system is designed to be 'biased' to the 'control' side….
at start up the 'control' should receive full operating vacuum FIRST and thus 'send' the signal to the actuators (servo side) to remain where they are.
If that doesn't happen the 'actuators' receive full vacuum FIRST and open the door (wiper door and/or headlight doors) until the 'control' side relay signals them to close again.
This is because the 'fail' condition for the system is for the doors to open.

For the wiper door look for a leak:
check valve
filter
wiper door relay
small hoses"

Good Luck e !
Regards,
Alan