1988 Mercury Marquis lights

You can go here for a printable full schematic of the lighting system.

https://www.2carpros.com/articles/mitchell1eautorepair-car-repair-manuals

The system in yours is strange, has relays for running lights and they go to a LCD dimming relay also under the dash. Might want to consult the diagram for yourself, would be easier if you saw what i mean

from what I can see it appears the tail lights get power from two sources.. once from the switch and also from the auto lamp relay. It appears from my limited experience that if the auto light relay is not closing the circut to the taillights that the taillights would not work in the auto position or the on position . is that correct???

have you ever replaced the relay ? where is it located?





[quote:0b475eb2ab="holtkb"]Electrical problem
1988 Mercury Marquis V8 Two Wheel Drive Automatic 158000 miles
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I have aproblem with the parking lights. The light switch has an auto on function with a light sensor in the front dash. I have replaced the origianal switch and problem still exists. I am looking for a detailed wiring diagram and advice.

The parking lights do not come on with the headlights in the automatic setting. The parking lights do not come on with the knob pulled clear out to turn the head lights on. With the knob pulled out half way you can get the parking lights to turn on. iIf you pull the knob out half way to get the parking lights on AND turn the headlights to automatic you can have both light sets of lights working. The problem stayeed the same with both the old ond the new switch.[/quote:0b475eb2ab]

Yes, that would make sense. It is located under the left side of the dash near the steering column....sorry to be so vague, that is all the locator says.