Just curious...should the hideaway lights on a 68 RS only open/close when the engine is running?

Thanks.

Yes, in conjunction with turning on/off the headlight switch.
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I believe if the system holds vaccum properly you should be able to turn on the lights with the engine off and have the headlight doors open. Maybe only once but the reserve tank should make it possible.

Dennis is right, I just redid my system and with engine off, about 30 min. later, I can still have enuf vacuum to open and close both doors. But only that one time in a cycle and the vac is used up. Its fun when it works :)

Thanks!