Hi folks,
I'm the new owner of a '95 850 Wagon. Among some other issues that this beast came with is a set of weird wiring issues.
To start, the brake switch is fine
Right now, if the headlights are on and you press the brake, the licence plate lights go out.
As well, the center brake light isn't working. Seems like it could be the wires through the hinge. Any other possibilities?
Thanks,
N

 

a good resource is volvowiringdiagrams.com I think you're on the right path assuming there's a short or open in a cable or connector that is related to the circuits to the bulbs in question. Does it change if you pull out the bulbs for the brake lights? all the fuses good?

 

If the center brake light can prevent your tag lights from working, then that tells you they are grounded together and this ground is disconnected. When you are not using the brakes, the tag light is still working because electricity can flow through the tag light, then backward through the center brake light to "escape", then forward through the side brake lights to ground. This does not cause the brake lights to light up because it's not enough power. I hope this makes sense. It's a very common problem with cars generally (not just Volvos). I did not bother to look at the diagram and verify how these are grounded.