Brake lights

[Eggert]

Hi guys,

I have a '01 4.4 which only shows left side and center brake lights when brake pedal is pressed. Lights are few months old so there's no corrosion in the way here. I don't get current on the right side plug for the brake light, however other lights on that side work though, it is only that one brake light which is out.

Anyone have any idea what could be causing this or a troubleshooting suggestion?

[jdstrickland]

The obvious thing is a burnt out bulb.

The first rule of electricity, be sure the bulbs are good. Take the known-good bulb and move it to the spot where the bulb does not work.

Keep in mind that the bulbs fit into holders that then screw into sockets on the tail lamp housing. You MUST put the right bulb into the right holder, and the right holder into the right socket on the housing -- where right means correct, not the opposite of left.

[jdstrickland]

Left and right brake lamps get a different fuse. You can have a blown fuse.

[Eggert]

Originally Posted by jdstrickland

The obvious thing is a burnt out bulb.

The first rule of electricity, be sure the bulbs are good. Take the known-good bulb and move it to the spot where the bulb does not work.

Keep in mind that the bulbs fit into holders that then screw into sockets on the tail lamp housing. You MUST put the right bulb into the right holder, and the right holder into the right socket on the housing -- where right means correct, not the opposite of left.

Sorry for not mentioning it - but of course I have checked bulbs and there's a new and working one in the socket for my right brake light.

[Eggert]

Originally Posted by jdstrickland

Left and right brake lamps get a different fuse. You can have a blown fuse.

I had researched this prior to making this post - and as far as I could see both left and right brake lights are on the same fuse; fuse #9 in the glove compartment. Are you sure about both brake lights having individual fuses?

[jdstrickland]

Did you swap the left and right bulbs to see if the problem with illuminating them changes with the swap or remains the same? If the problem follows the swap, then the bulb or holder is the trouble, if the problem remains the same then the vehicle is the problem.

There are 4 screws holding the tail lamps in the car. On the E36 (3 Series) cars, there is significant trouble with the ground wire on the tail lamps burning up -- physically getting hot and charring. I don't know that this is a problem for the E53 or not, but the inspection is easy. Unplug the wiring harness at the tail lamp and observe the condition of the connector pin where the BRN wire is. If charred, then you found the problem. The cure is to establish a new ground path.

[jdstrickland]

Maybe I was thinking of the running lights getting different fuses. Sorry. I do not have the Bentley manual for my X5, so some of the things I say are said because the E36 and E46 do stuff that can be assumed to be done the same way on the E53.

The left and right side tail lamps are on different fuses, not the brake lamps.

[Eggert]

Thanks for your willingness to help jd.

But when I unplug the taillight and measure current from the 4 pin plug, (one ground and 3x + for each light; daylight, turn signal and brake light), I only get positive current for the turn signal and daylight. None for the brake light. So logic tells me it has to be something other than the taillight itself, right?

[Eggert]

Maybe I should also mention that my taillights are brand new, some ebay stuff previous owner put there. But it doesn't change the fact that no current goes to the plug when brakes are pressed.

[Tomaz]

Originally Posted by Eggert

Thanks for your willingness to help jd.

But when I unplug the taillight and measure current from the 4 pin plug, (one ground and 3x + for each light; daylight, turn signal and brake light), I only get positive current for the turn signal and daylight. None for the brake light. So logic tells me it has to be something other than the taillight itself, right?

Right, if no power is at the connector than the problem is not the bulb or tail light housing. You should find a wiring schematic and follow the wire back to the spice or next connections until you find the break in the circuit. Good luck.