I am out of ideas and am looking for some advice. I have a 1988 240 DL Sedan and am having brake light issues.

The problem is; When the headlight are on, the brake lights come on and when you press the brakes, the third tail light comes on. When the headlights are off, the brake lights work just fine.

Here are the steps that I have already taken:

1) I made sure that the fog light switch is working and is turned off.
2) I have replace both light bulbs with new and correct bulbs.
3) I have replaced the Bulb Failure Unit (The red cylinder under the drivers dash).
4) I tested the Bulb Failure Unit socket with a voltage tester to ensure power is going to the unit when brake is depressed,
5) I tested the Bulb Failure Unit Socket by jumping pin 9 and 10 and 9 and 11 and the correct brake lights came on.
6) I have not tested the brake switch since the bakes lights work when the headlights are off.
7) I have cleaned off the light sockets to ensure good contact.

The only step I haven't taken is to hard wire the tail lights.

Is there any additional steps that i can take?

Thanks,

Aaron

 

commonest cause of lights crossing up like that is bad grounds.

 

I think you mean third brake light not tail light. Find your wires coming from the right and left brake light and inspect those and make sure they arent connecting to your headlights through an open wire between the two thay might energize your brake lights at the wrong time. Worse case scenario if bad wires ir ground arent found you will have to piggyback the outer brake lights to middle brake light if you are sure it always function at the right times.