This 2004 Volvo XC90 came in with multiple problems and this one was that the lower stopllights do not work. The upper CHMSL works. Of course the problem cold have been that both lower bulbs were blown but I had checked one side when I had the light assembly off for another reason. Since the CHMSL was working I knew that I did not need to check the stoplight switch or the input to it.
I also took a minute to look at a wiring diagram and knew that all of my test points were located at the rear of the vehicle. The first step is to lift the rear floor cover and move it out of the way. There are two cable hold downs on either side with slots in them.
They have to be moved so that the larger hole will lift off of the peg.
Then the whole panel can be moved out of the way.
There is a small wedge piece to the left side of the vehicle.
It lifts up and out of the floor.
Now by lifting up and pulling slightly to the center of the vehicle the side panel will move. Then it has to be dropped down about an inch for the upper retainers to come free.
Now we can access the rear fuse/relay box for testing.
With the brake pedal depressed, fuse number D14 should have power on it. It does not so we have to do further testing. It receives it’s power from the contact terminal #3 of the stoplight relay. It also passed through the brake light shunt on it’s way from the relay to fuse #14. By the way there is a fuse position label on the rear edge of the fuse box.
Fuse D3 should have power on it at all times and it does. It supplies power to one of the contact terminals of the stop light relay. Terminal #5.
I could not find the location of the brake light shunt so I concentrated my efforts on the stoplight relay. I did not want to take the whole inside of the vehicle apart to access the relay so I cheated a little. I lifted the upper lock for the fuse box.
Then pushed it towards the outside of the vehicle. This gave me a little bit more room but not quite enough.
I folded up a cloth fender cover to protect the plastic and used a long pry bar to gain a little bit more room.
The stoplight relay is the blue one in the next picture. I am assuming the long thin plastic pieces installed in the fuse box are the various shunts for the vehicle systems but my information software does not identify them. They appear to be relatively fragile so do not apply pressure to them. Also the relays are very difficult to pull out of the fuse/relay box. I had to first remove the relay above the stoplight relay before I could get a good enough grip to remove it. Even then it took several tries and some painful finger tips.
I did prevail against the relay and was successful in removing it without having to remove more interior panels.
The old relay on the left and the new relay from the Volvo dealership on the right. Even though both parts are made in Portugal they have different part numbers and design variations. The most obvious of which is the color. The blue one has the word Volvo on it and the black one has FoMoCo on it.
The relay installs in this position in the fuse/relay box. The two larger terminals towards the front of the vehicle.
The new relay installed. It was much easier to push it back in than it was to pull the old one out. I also re installed the other relay that I had removed earlier.
We now have power on the D14 with the brake pedal depressed.
Now the lower stoplights work as they should.
On to the next problem.