Mercury marquis 2003 tail light doesn't lit on. bulb is fine.

if it was just your brake lights i would say its the brake switch. if you have checked all light fuses next step would be checking the bulbs. if bulbs are good check continuity with a test light.

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From That Light There Is Only 2 Wires , Trace Them Back To The Tail Light Connection - Most Likely A Split Wire Or Bad Connectio

Check the headlight switch...been know to fail and no tail lights

You can get the lights from the trunk

check your bulbs brake and tail light the same bulb ?

Look for the easy things first. Could be one bulb was burned out and then the other burned out. Check the bulbs. If that doesn help look at the fuse block, probably under the dash on the driver side. If the fuse is the problem and if it blows when you put in a new one. look in the trunk at the tail light wires to see if they have been damaged or have come loose from the bulb sockets and are causing a short that blows the fuse. Repair or replace bulb sockets and or wires. Good luck.

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Gaker

it can be a few problems but i would start by checking the fuses. after that look under the dash where the brake pedal is. you will see a switch there that toggles on when you apply the brakes. i have to mention one other thing because i've had experience with it. check to make sure the bulbs are good. unless your car is equipped with a warning system or you check the brake lights often they may all be burned out over a period of time without you knowing it. a small trick to that is whenever you are backing up or near a something that you can see the back of your vehicle... apply the brakes... if you don't see lights on one or both sides it's time to start changing bulbs.
the tail lights working is independent of the brake lights as generally if it's the same bulb it will have two filiments.

Move trunk interior inside fenderwell. There are 4 retaining nuts that hold the outer light assy. Remove those nuts and pull assy straight out so as not to damage plastic studs. Rotate bulb socket counterclockwise and and replace with correct bulb

It will either be a broken wire under the rear of your car where gravel sones hit a lot, or bad bulbs. Yes, they are the same bulb for tail lights as brake and hazard and signal, but they have 2 filaments. One is for the tail lights, the other for the rest. A test light is the simplest way to check it all out.

does the Center brake light work ? I think your looking at replacing the brake light switch !