My 84 242 had non working rear tail light when I got it. All other lamps worked.
Turned out someone had put in a 21 watt lamp in place of the 5w. The flexible circuit board had been burnt at the connector.
When I went to the junkyard, it seemed most of the tail lights had too high wattage lamps in them. The red lenses were discolored or bulged from the excess heat.
I finally found a decent taillight assy. from an 89 or so. I also took a flexible PCB from an 88 or so 240 also.
After installing in the 242. I discovered the outer-lower 5w bulb would not mount in the hole. I realized that when Volvo added rear fog light (not on my 84 242), they added the fog to the upper inner spot, and made the outside lower spot a combination tail/ brake light.
Although wiring exists for a fog in my car, there is no dash switch.
So I decided to modify the newer PCB to work as the older one did. This would allow me to, plug the 5W bulb into the outer lower position .
With 2 cuts and 2 jumpers I modified the newer PCB to work as the older one had.

I have a picture but am unsure of how to load it so others can see., can send though if some one needs it.

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744 & 745 16v 4+OD, 245 SE auto, 242Ti 4+OD, 245DL auto parts car