99Windstar brake lights out

My sister's windstar is possessed. It has more electrical problems than I can post. The latest is that both lower brake lights are not working but the upper one still does. Bulbs are good and sockets look ok. Can anyone tell me where (How to get to)the 3 way splice is for those three lights? and what color the wires are? Thank you for your help. P.S. I've owned 3 ford trucks and still am a ford man. My name is 98 suburban because I've has problems with the wifes.

Remember that the external lamps get 12 volts "all the time" ... unless a fuse blows or a relay messes up. Its the ground side that gets switched ... in the case of the rear lamps the ground is switched by the Rear Electronic Module (REM).

Anyway, the "constant 12 volts" goes through "switched system power relays #3 & #4".
... and for the upper stop lamps, then thru fuse #12 and wire colored RD/LB
... and for the left rear stop lamp, then thru fuse #7 and wire colored GY/RD
... and for the right rear stop lamp, then thru fuse #13 and wire colored RD/YE