Hi everyone, this is my first post. I have a 69 Camaro that has the vacuum operated hideaway headlights. The headlight doors do not work. I have replaced all the hoses and they still don't work. How should I go about trouble shooting the system to locate the problem? Thanks!

Look in the tech reference section of this site for the system hose diagram. Then check for vacuum at the actuators. the vacuum should change between the two hoses that are connected to the actuators as you cycle the headlight switch. if it does then suspect a mechanical problem. if not, back track up the system and hoses to determine where the vacuum is not flowing properly.
sorta like electrical system diagnosis.
TTFN
Mat

you may also have a problem with low vacuum at low engine speeds. I know mine does; do they close when rpms are elevated to 3 -4k? If so, you may want to check into placing a vacuum check valve to prevent "bleed off"...