This 1997 Ford Explorer came in with the complaint that the dome lights would stay on with all of the doors closed. I tried using one of my scan tools to look at data for the door ajar switches but was only able to see the information for the driver’s door and the passenger front door.
The next two pictures are more to provide a temporary means of disabling the lights so that the battery will not go dead. The first fuse is #27 and the second one above it, is fuse #23. Removing both fuses will prevent the battery from going dead. Although both fuses are powered, the power comes from the battery saver relay in the under dash fuse relay box. If all of the doors are genuinely closed the body computer will turn off the control circuit for the battery saver relay and there will be no power on either fuse. It can take up to one hour for the relay to be turned off.
The battery saver relay is the second one, up from the bottom, on the right hand side.
If the relay center has never been into, there will be securing tape that holds the cover in place during vehicle assembly. It has to be cut/torn before the cover can be removed.
Since my scan tool was of little help I had to go old school on this one. The best place to test the door ajar switches is at the Central Timer Module (CTM). It is sometimes referred to as a Generic Electronic Module (GEM). It is located behind and to the left of the radio. The tools I am holding below are needed to remove the radio.
They insert into the four holes in the radio face. Once they are fully seated, they have to be flexed outward towards the doors and then grasped and pulled towards the seat. The radio should release and pull out. It can take a couple of tries and you may have to do some wiggling. After removing the radio disconnect the harness connectors from the radio.
There are two screws with 7 mm heads that have to be removed. One on each side, above the a/c controls. If for some reason you do not have the above tools, the radio will come out with the panel. It takes a little bit more effort and care doing it that way though. The weight of the radio has to be properly supported or the panel/dash can be damaged/scratched. Also it is a little more awkward to disconnect all of the wiring harnesses.
Then grasp one edge of the trim panel and pull it loose from the dash. You will need to disconnect the lighter wiring and any other wiring on that side.
Then the panel can be left hanging on the right side of the dash. If you do not want to disconnect the rest of the wiring. The CTM or GEM is located to the left of the opening.
The center duct work needs to be removed to gain access to the CTM. There are two 7 mm headed screws that have to be removed.
Then the duct work can be pulled from the opening.
The CTM and connectors. The connector that I needed was the very top one.
I pushed in the thumb latch and pulled the connector from the CTM. It took a little bit of wiggling to free it. Then I had to manipulate it around to get it freed from the rest of the wiring.
There are several wires that need to be checked to test all of the door ajar switches. The white/purple wire that I have my pick inserted into is for the rear hatch and the rear tailgate switches. All five wires listed below are in order going up the connector. With the doors closed there should be no circuit to ground. With the doors open there should be a circuit (continuity) to ground.
White/purple = rear hatch switch and two tailgate switches
Light Green/yellow = left rear door switch
Pink/light blue = right rear door switch
Gray/red = right front door switch
Yellow/black = left front door switch
I have to note that the order for the pink/light blue and the light green/yellow may be reversed. In the wiring diagram that I looked at, they have the terms reversed at either end of the same wire.
With one lead connected to my test probe.
The other connected to a good ground. In this case the ground wire for the lighter.
The meter set to read ohms and there is a resistance of .19 ohms. With the tailgate closed it should have read infinity. On my meter that is displayed a OL. So I either had a faulty switch or the wire was shorted to ground. I removed the interior panel on the tailgate and unplugged each switch. One at a time. Until I had an open circuit. Then I re connected the switches one at a time until the short to ground returned. Of course I had to close the tailgate or the hatch in between each switch re connection.
The right side tailgate door ajar switch would not switch to the open position. I found a couple of things wrong at the tail gate. First of all the latch assembly was very dirty and I could not make it latch by hand. I tried to order a new one, but they have been discontinued by Ford. The picture below is of the left tailgate latch assembly because I forgot to take a picture of the right side latch before I cleaned it.
I removed by removing the three attaching screws. I also had to remove the tail gate interior panel and disconnect the electrical connector and the linkage rod that attaches to the handle assembly. Sorry no pictures. Then, I soaked and scrubbed it in my cleaning tank. After drying it, I coated the surfaces with a lubricant that leaves a film, that is supposed to not attract dirt. Then I worked it back and forth until it freed up.
I also had to remove the striker bolt and install a new plastic bushing as the old one was broken. I suspect that there were pieces of the broken bushing in the latch assembly.