[m1kemcc]

Sometimes my brake lights (all three) come on by themselves. Sometimes my L dash turn signal indicator comes on when I apply the brakes, but will clear if I adjust the turn signal switch position, and it always goes out when I take my foot off the brakes. The L turn indicator always works properly, even when braking.

On rare occasions my L marker lamps will be on with the engine and all lights shut off. I just had to recharge my battery because of this. I thought perhaps a bad ground on my trailer harness was causing this, but I just had that rewired, and it did not resolve the problem.

I've had this problem since I bought the Jeep several months ago. I have to wonder if I have more than one problem going on here?

[Mean Max]

Sounds like a common problem. The tail lights (all, brake, turn, reverse, & park) all ground through the screws holding the tail light housings to the body. Sometimes the ground connection isn't so good. Usually just removing the lense cover, then removing & reinstalling the screws one at a time will improve the ground.

Your problem seems to sound like a bad ground is causing the power to "back-feed" through the other circuits "looking" for a place to ground out. Being as the left turn signal indicator light is the one coming on, my money would be riding on the ground being poor at the left rear tail light mounting screws.

Max

[Jasen]

What Max said.

Also, if the brake lights come on by themselves, that might be a switch adjustment issue. I'm guessing your 99 takes the same brake light switch as my 98, which menas there is no adjustment. By hand push the pedal and let it up slowly, check if lights are on, if so pull up on brake pedal and check lights. If out you probably need to tweek the bracket. You have to grabe the switch bracket with a big pair of channel locks or the like and bend it towards the floor a very little bit, then actuate the prdal slowly by hand.
Just went through this with a new switch.

[patduke90]

Mine does the same thing. You can try taking off the switch and cleaning it inside or you can just learn to live with it like I've done. Mine actually got rained on and worked correctly for a few days, but it eventually went back to the broken status.