Brake lites
You can get "tricked" down the wrong path by bad grounds at the sockets or SHORTED BULBS. (Or wrong bulbs) Bulbs can "burn" inside and the remnants of one filament can fall over and weld to the other. This can produce interesting results....like both lamps blinking when the opposite flasher is on, etc
So try this........pull out both rear bulbs. While out, test them on a battery for both filaments.
Then access the turn signal connector coming out the column. Consult the factory manual for the colors
You have flasher power going IN. This is hot with the key in "run" You can jumper the flasher socket if necessary
The brake switch power is going IN, this is hot anytime the brake pedal is depressed.
Check both those are present on both sides of the connector
Then check the rear two wires going out to left and right. You should have power on both wires when brake is depressed, and power on left or right when the switch is in appropriate position.
MAKE SURE the 4X hazard switch is "off"
You can download free service manuals over at MyMopar. Some of them came from the guys here at FABO
http://www.mymopar.com/index.php?pid=31
Below is the TS switch
The top wire, an 18ga White, is stop light switch power going INTO the TS switch
Fourth wire down, 18ga Red, is power going in from the TS flasher
Second and third, BRown and GreeN are the left and right rear turn / stop lamp wires
From there, they go down to the connector for the rear harness in the left kick panel, then to the rear