|08-26-2019, 04:54 AM||#1|
Flirting With TSL Addiction
9-5 Wagon Tailgate Latch Microswitch Fix
If your 9-5 wagon has an issue with the light not turning on in the trunk /cargo area and the tailgate not showing up on the "open door" diagram on the instrument cluster, the microswitch that is inside of the latch itself may be your issue. It has been the cause of this problem in 2 9-5 wagons of mine now, so I came up with another solution that is more permanent than a used latch. This issue is separate from the trunk wiring that causes issues in 9-5 sedans, however don't rule this out when diagnosing your problem.
To bypass this issue, I decided to simply use a different switch to indicate whether the trunk was open or closed. I had a bunch of door switches laying around from my 9000's, so I used one of them. You can mount the switch on the tailgate right next to the latch. You simply tap into the factory connector that goes to the latch inside the tailgate.
However, I wanted my switch install to look as factory as possible, so I went a more complicated route and mounted my switch on top of the cargo opening; underneath the plastic trim moulding. I will outline what I did for anyone else interested in using this as a solution.
I'll note that I tried simpler solutions to avoid doing all the wiring. I tried shorting the switch connector wiring so that it would always be "on" and then tried using my switch mounted in this location with the wiring running locally to the ground on the light itself. The car did not like this. The light worked as it should, but the car still thought the tailgate was open and the two smaller lights on the tailgate corners would stay illuminated even when the tailgate was closed. To make everything work properly, you have to have the wiring go to the factory location for the microswitch.
The finished product:
Start by removing the tailgate panel by pushing out the pins and removing the two T30 torx bolts that hold the interior handle on. Remove the top plastic panel and side panel (the left side in my case) by carefully prying in multiple places until it pops off.
You will also need to remove the center plastic piece that is just below the 3rd brake light and above the weatherstrip seal. Pry the circular caps out with a small screwdriver and remove the two 10mm bolts that hold it onto the car.
At this point, decide where you want to mount your switch. I went with a spot next to the left hand tailgate hinge. I wanted to be close to the hinge to minimize the amount of wiring needed and it also seemed like the best spot to ensure contact with the tailgate when it was closed. Be sure to mount it somewhere that the switch will have room to slide backwards a couple of mm and not ground out on anything metal. The 9000's switches operate by physically sliding backwards into the body of the car a little bit as they are depressed.
Drill a hole big enough to accommodate the switch pins and body. Drill a smaller hole for the mounting screw. (I used a lag screw similar to the ones that are used to mount these for the doors)
The switch mounted above tailgate:
The back of the switch inside the ceiling of the car:
This is an outline of the path I took with the wiring to get to the switch connector for the latch.
Passing the wiring underneath the left hand hinge to be out of the way when closing the tailgate:
I pulled the factory wiring out of the channel in the hinge and laid my new wiring underneath the factory wiring to make sure the new wiring was protected. Make sure to leave enough slack in the ceiling side of the wiring to ensure that the wiring doesn't get stretched when opening and closing the tailgate.
Continue routing the wiring up through the hinge and into the body of the tailgate. I stayed on top of the factory wiring harness at this point to avoid making contact with any sharp edges on the body. I used small zipties to keep the wiring in place.
After you're past the hinge, just follow the factory wiring harness on the left hand side of the tailgate until you get close to the latch wiring harness using a ziptie every couple of inches to keep everything neat.
I separated from the factory harness right after the green connector and cut over to the latch connector. I found an extra clip that clips the connectors to the tailgate and secured the remaining wiring with zipties. I had an extra connector laying around that was the same type as the original, so I wired that into my new wiring and plugged it into the original latch connector.
Once everything is wired up, test and make sure everything works as it should.
To finish up, I drilled a hole in the overlying plastic moulding so that the switch would be covered up, but the part that gets depressed would still stick through. For better contact with the tailgate, I got a set of assorted vacuum line caps from a local autoparts store, cut them down and put on top of the switch. It also cleaned up the look pretty well.
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-1992 9000 T5
-1994 9000 Aero
-2004 9-5 Aero Wagon - Espresso Black
-2004 9-5 Aero Wagon - Glacier Blue
Last edited by Troup; 08-26-2019 at 06:05 AM.