On a 1986 240 Wagon:

With all lights seeming to work OK, depressing the break pedal causes the right taillight to extinguish and the companion Break light does not illuminate.

The Left Break light and the center/rear window break lights do come on.

My son-in-law followed a car today that ...

Chris,
Thanks!

Both the 240 and 740 wagons have foglight switches on the dash. The cars belong to my Daughter and her husband and are relatively recent purchases.
Neither were aware of the existence of Fog lights. Now they are.
My only Volvo was a 197? 164 sedan.

It seems to me that rear Fog ...

The 1986 240 Wagon has a stack of lights at each corner on the rear.
It seems like:
top - Red - Taillight
next - White - Back Up
next - Amber - Turn Signal
bottom - Red - combo Break and Taillight

PROBLEM: The top lights on both corners (Taillights) do not light up
under any conditions.

Are ...