I have a 1989 240DL the driver side break light stays on when the head lights are on. when they are off the break lights work fine can you help?

sounds to be a grounding issue

Make sure all the bulbs are working in the turn signal. Some front turn signals will use two or more bulbs per side. If any one of these bulbs are burned out it will cause the turn signal to flash at a fast rate. It also could be a bad control lighting control switch a.k.a. multi-function switch.

change the light control module. it is located under the dash near your right knee on the drivers side. this is a common problem with crown vics.

If it is a tail light and only one side is out, it could be the socket the bulb goes into.

Over time corrosion can accumulated and rust out a tail light socket and render it non-functioning. Yes it can be replaced and in your case for about $6.00. You can find these at most any auto parts store.

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It sounds like a bad earth connection in the vehicle rear wiring loom. Check the earth wire that runs from the globe sockets in the light units and any connectors in the wiring loom near the light assemblies as well as where the earth wire is attached to the body. If necessary, remove, clean thoroughly by removing any corrosion or paint and re-attach securely.

Make sure you are fitting the correct bulb.And check your brake light fuse on some cars they have a seperate fuse left and right.

Hi and welcome to FixYa,

Almost always, your described concern indicates a loose ground particularly on the driver side. What is required is to check the connectors leading to the driver rear side and/or a ground wire. Often, the problem would be the ground terminal is loose or corroded leading to the body of the vehicle. A temporary workaround is to determine which is the ground in the bulb socket (always the body) and wire a jumper wire to any exposed metal part of the rear end.

Good luck and thank you for using FixYa.

The fuse box is located under the dash board on the drivers side. I hope this helps.

1st get autozone to clear the code, (free) The only thing I can think of that goes out when car is off and on when lights turn on is the parking lights on the side, the wires could be touching in the conduit, start car and pull brake fuse out, if the lights stay on you have a short, if only the park lights stay on (double filiment) look at the lighting system, but if the brake and driving light stay on, sounds like an ecu problem.