Help with vacuum system

[rainman]

I need some help with the headlight and wiper doors. When the engine is running the headlight and wiper doors operate normally except for going down a little slowly. When the car is turned off the doors stay down, but every time that I start the car both headlight doors and the wiper door opens then closes by themselves. I have checked the headlight system for leaks and there appear to be none. There appears to be a drop in pressure in the wiper system but I haven't been able to isolate it. Has anyone seen this before or have an idea what would cause this problem only on start up? Thanks for any help.

 

[Rip]

Wow, that IS a strange problem. It's going to be interesting to see how this turns out. It sounds like a possible problem with the vacuum hose routing. Another thing that comes to mind is a problem with the manual override switch (pull down switch) under the steering column.....like maybe the two hoses going to it are crossed, or maybe not plugged in. Did this problem just happen suddenly? ....or did it come on slowly over a period of time? Has anyone been messing with the hoses at the relays?

 

[RMS73]

Try checking the check valve. When I was having problems with my vacuum system I vaguly remember something obut the check valve leaking and upon engine start up the lights would raise and lower.
Roger

 

[Stallion]

Maybe it's the relays? That is kind of strange.

 

[rainman]

I recently purchased the car and it has had the problem since I got it. All the hoses appear to be correctly connected. I've checked the relays and the best that I can tell they are good. I checked the check valve this morning and I think it's bad. As soon as I can get one I'll put a good check valve on. Hopefully that will fix it. Thanks for the info.

 

[Stallion]

A valve problem seems like it could do this, but just the way it functions. I don't understand why they flip up and down. :confused That's weird functioning for an un-functional function. :confused

 

[Rip]

I guess a bad check valve could somehow cause wierd things to happen. I'm not familiar with the systems that include wiper doors. I actually ran without a check valve for a while on the 74. In theory, all the check valve does is hold stored vacuum in the tank so the lights/wiper door can be operated with the engine off. The fact that they open then close on their own is what confuses me. The relay is somehow sending vacuum to one side of the actuator (open) and then to the other side (close) . The relay should only be directing vacuum in one direction..... depending on wheather you are turning your lights/wiper on or off.

If the problem still exists after the new check valve you may want to verify that the routing of the hoses is correct. Here is a diagram of a headlight with wiper door system.
http://www.stingray.nu/bilder/vacuum.pdf

Note...on this diagram.....where it is supposed to be pointing to the check valve, it appears to pointing to a relay.

Hope this helps

 

[CS72Roadster]

I cant completely explain the how's and why's but I just fixed the same problrm on mine...vacuum check valve.

CS

 

[rainman]

Thanks for all the information. I got my new check valve today and the problem appears to be fixed.