QuestionRoland-
On my 96 COncorde, my interior lights started staying on constant a few weeks ago. I have pulled the fuse in order to be able to drive it, but also lost stereo, electric locks, etc. when I did so.
The door switches have all checked out fine. I do know that in the fuse box inside the car, there is a 10 amp fuse, will have to check the # of the slot for sure. In the computer box under the hood, slot # 20 (I believe) is the brake lights and interior lights.
While removing either fuse or relay does shut off the lights, that is about it. At the moment, in order to be able to still use the car, we have removed the fuse in the inside control panel.
(No, it's not the dimmer switch left on, that is one of the first things I checked.)
We have been told by a tech that it is most likely the BCM, however, upon locating it under the center console kick panel, we are lost.
What do I need to do here? I am at the point that I am ready just to pull all the bulbs out and run it that way!
Babette
AnswerHi Babette,
The fuse that will kill all the interior lights is #13 under the dash. That fuse sends power to all the lights, but they don't illuminate unless the other end of each bulb filament is connected to the - post of the battery (ground)
The way the system works, instead of having switches that activate the lights by grounding the return path from the bulb directly, the switches are connected to the body computer and the body computer does (mediates) the grounding. There are two possibilities;
One of the many wires from the bulbs to the computer is grounded due to a short in a wire or a bulb socket OR the body computer has failed in its mediating function and is grounding the return wires without any reason to do so. The way to check the first possibility is to pull the bone colored plug from the computer and find the pin 12 (which is supplied with a yellow wire) and see whether it reads 12V when the fuses are all back in place; measure between the pin and and any shiny metal body part near by. If it reads 12v then the possibility of their being a short to ground is eliminated. If it doesn't and instead measures 0 ohms to ground then you have a short. The way to find that is to start removing bulbs one at a time until you find one that eliminates the short or raises the voltage to 12v. Then examine that bulb and the yellow wire at the socket for any sign of a ground. Another way of testing this is that if, when you pull the bone plug, the bulbs go out (which I presume will be "on" even with all the doors closed) then that means the problem is not with the wires but with either the body computer falsely grounding the wire or a false switch "report" to the computer to ground the wire eventhough you haven't done anything (e.g. opened a door, turned on the dimmer to the interior lights on position) to tell the computer to ground it. That will take a bit of sleuthing to sort out.
So let me know what happens when you have the fuses in and pull the bode plug. Do the lights go out?
Roland
