Do they open when lights turned on? Thats pretty important to help solve
If they open with lights on, engine running it's likely a leak.
Work your way back from the door (the headlight assy) actuator.
One or both of actuators, tubing to it, the control valve, may be leaking
vacuum, or the control valve itself bad.
Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!
The headlamp doors are vacuum operated and open when vacuum is removed. There
leak somewhere in the system. You have a vacuum supply from the engine, a check
a vacuum chamber, a valve on the headlamp switch, and an actuator on each
door. Visually inspect all of the rubber vacuum hoses for breaks or cracks,
leaks (hissing) near the actuators, switch, reservoir, and all connections. Make
the check valve only passes air one way. At this age it could be any of the
back when this car was newer the headlamp switch and the check valve were common
There may also be a manual valve under the hood, I don't remember if this
Tbird had one.
If there is a leak, the engime will likely idle rough. If the check valve is
defective, the engine will idle normally but the doors will open as soon as the
is turned off.
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