Dome light stays on and drains battery
Many late model cars have the door light switch incorporated into the door latch. If the switch gets dirty or gummed up, the body control module thinks the door is still open and the dome light stays on.
Gummed up door switch is the cause
Remember the pin/plunger switches that car makers used to install in the door jamb? Well, when you opened the door, the pin extended and lit the dome light. So the dome light stays on as long as you leave the door open. Well, Ford eliminated the switches in the door jamb and instead installs the switch in the door latch itself. It’s located right under the door latch mechanism. When the door latches, a lever pushes against the door switch plunger to signal the body control module to turn off the dome light. Good so far….. The problem is that the switch gums up with grease from the latch mechanism or corrosion. That’s when interior lights stay on.
Some shops have reported success by saturating the latch mechanism with a rust penetrant and opening and closing the door about 20 or 30 times.
That works the penetrant into the mechanism and some of it finds its way to the lever and switch. You really don’t have much to lose by trying this method because the only alternative is to remove the door trim panel and replace the switch.
I’ve tried this on a few Ford vehicles and had success. However, it’s not a long term fix. You will have to do it about twice a year.
© 2012 Rick Muscoplat
Posted on by Rick Muscoplat