I have a 68 camaro rs, and am also having trouble with the headlight doors, I can hear a vacuum leak at the switching valve on the tank. Is this normal or not,also is there a way to isolate the canisters and check to see if they are working. I rebiult the doors with new bushings, while I had the canisters off I tried hooking them to a vacumm source and only one of them worked. when i put them all back together nothing works. They both appear to be original, can anyone tell me where to get a vacuum diagram and a little insight as to how this system works THANK YOU