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1976 Mark Headlight Issues

Bill –

Turned light switch on for night driving and the doors opened . Now they will not close . Changed headlamp vacuum check valve (metal 3 port nos.)connects to steel air tank reservoir. Reservoir holding air as I removed the single rubber hose from the 3 port valve. Removed the rubber hose from the single door motor on the right hand side of the car in the bottom of the grille area and their was no vacuum. The 4 port check valve on the DS. fender has not been checked or replace. The headlight switch is the one with delay and automatic turn off which I have never used. Looks like a very hard job if the switch is my problem as I am not a mechanic and just being self taught on a lot of my cars.

Thanking you in advance,



Greetings Tom –

The vacuum operated Headlamp doors are a popular fail/repair item on vintage Lincolns. I do not know if yours were open or closed when you started the car or if your car sits idle for long periods of time etc. Because there are so many locations to test you should begin with the basic (easy to check) items first in my opinion. Because you do not use the automatic system, the only part that you operated was the headlamp switch. I would begin by testing for vacuum at the h/l vacuum motor with the engine running for correct vacuum from the h/l switch with the switch off and then on as required. If the h/l switch is sending the correct vacuum to the h/l vacuum motor in the on and off positions the vacuum motor itself would need to be tested with a hand held vacuum pump. The vacuum motor or linkage could be seized or the vacuum chamber ruptured. With loss of vacuum to the vacuum motor the doors will automatically open as a safety feature. Before performing any of the above tests, you should first perform a visual inspection test on all of the related vacuum lines. I am assuming that the system was working correctly at some time for you and that no one has tampered with the vacuum line installation. The above are only suggestions for locations to begin your testing. Mechanics that work on these types of problems learn from each step of the tests so that they are led as quickly as possible to the failed area. When you or your mechanic have more information or need any schematics or parts, please call your Lincoln Land parts specialist for further advice. We wish you a speedy and correct diagnosis.



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