I recently bought a ’79 Lincoln Mark V with the headlight doors nonfunctional. The doors will stay closed when the motor is running and will open when the motor is off. With the guidance of your blog I have narrowed it down to the vacuum module (I believe its called) and found it is disconnected but cannot find where it connects back up to. Here are pictures of the module. I was wondering if you know where this might connect to?
Your email indicates that a previous owner or mechanic has possibly disabled the ” Autolamp” system on your Mark. To what extent I can’t tell from here. This is usually done in frustration because of a fault in the system. Your first photo is the vacuum control module with three vacuum lines unplugged. They should be near by or the previous owner may have eliminated them. Your second photo is unclear but could be the electrical connection for the Autolamp amplifier. It may have been removed also if it is not near by. In any case you will require the Shop Manual to test the various components. The manual is excellent for these tests but seems to be lacking in vacuum schematics. If the previous owner has turned the system into a manual setup you should consider repairing it to operate correctly as such and then repair the automatic section later. The shop manual is helpful for this repair also but you will need to study it and be familiar with the operation of the various vacuum operated components in order to do the proper diagnosis. Headlamp doors that open shortly after the engine is turned off indicates rapid vacuum loss. Popular fail items are ….Leaking headlamp vacuum motors, vacuum check valve, vacuum reservoir, headlamp switch and any position that the vacuum hoses are routed to. Unfortunately, this diagnosis and repair could be challenging if you or your technician is inexperienced and unfamiliar with these systems and even more difficult if some needed parts have been discarded by the previous owner. We wish you good luck and if you need help with any repair parts, please call our office.