I hate the vacuum system on these c3's. I have just finished putting in a completely new vacuum system including new hoses, actuators for the headlights and wiper door, and three brand new gm relays. I started the car up and the wiper door opens fine but will not close! What am I missing? What is that "thingy"(for a lack of a better word) that is mounted in the cowl area where the wipers and wiper transmission are? Would that have anything to do with it?
Thanks :confused:

 

You will have to remove the vent screen between the wiper door and the hood, on the passenger side, there is a vacuum valve that the wiper arm has to depress so the system knows the wipers are in a "parked" position and it is safe to close the doors. I have found more than one time that the wiper arms have been removed by some "goober" and re-installed in the wrong position. There is also a vacuum bleed hose comming out of the grommet in the firewall by the passenger side from this valve and oftentimes someone plugs the hose making the system not function. The vacuum actuator also can have a leak at the front grommet plug (GM put the plug there to allow a manual override of the system by removing the plug and pressing directly on the actuator piston from the plug's access port to open the wiper door.) My wiper door has worked for more than 8 years since I fixed the system, I can raise and lower the door with the engine off if the car has not sat for too long, same for the headlight doors. The actuator valve can have problems also causing the system to fail, the front vacuum port is the one where vacuum is applied to shut the door, you can hook it directly to the intake source for testing to see if the system will function, this will isolate you to the actuator and wiper arm valve assembly for potential problems. There is some good information in the 1970 Fisher Body manual for diagnostic troubleshooting. There may also be binding in the mechanicl linkage and hinge assembly that may require your attention. Email me if your still having problems after doing some of these system checks.