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Member Derek said the is an opening on the relay that acts aa a vent. Mud wasps or debris can block the opening so the rlays dont work.
Also...some light oil drops into all the ports of the relays could help the internal piston move freely.
You also have a one-way check valve and a vacum filter near the master cylinder that could ne clogged..they are inexpensive.
If you pull off the yellow striped (center) hose from BOTH relays and plug one of them off while attaching a vacuum gauge to the other, what vacuum reading do you get? You should get nearly the same reading as you have at the vacuum reservoir tank. If not, you have a leak between tank and test gauge; or you have some kind of blockage in the line. Disconnect ends of a hose and blow it out with compressed air, if you have a blockage.
If you find the vacuum is good with the above test, the relays need to be replaced or rebuilt (new O-rings and lube on the shuttle valve inside the relay).
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just disconnect one of the actuator relays and plug the lines and operate the other headlight. then swap the plugs and see if one is better than the other....you can narrow down the leak.
Or If you have a couple of tees take one relays out of the loop and and operate both actuators off one relay, it will tell you which relay is leaking. IF any of the hoses come off the nipple easy cut off a half an inch and reapply the hose
Headlight door relays
