Testing 1-2-3A few tests can quickly identify a bad signal switch, saving the potential frustration of putting together the column and tearing it down again to replace the switch. Here's how to test it:
Horn: The switch provides the ground for the horn relay. This is the black wire. Bridge a test light from the black output wire to a hot source. The light should fire when the horn is depressed, and if it doesn't, suspect a fault in the switch or horn contact plates. Substitute a multimeter for the test light by checking for continuity between the same wires.
Brake lights: The brake lights on Mopars share a common bulb with the turn signal and feed the brake lights through the signal switch. A failure in the turn-signal switch is a common cause of frustration when brake lights refuse to function (the signals may even work fine). To check for a problem in the column, center the turn-signal switch and run a hot jumper wire to the white brake-light feed wire at the switch connector. The test light should come on when contacted to the brown (right rear) and green (left rear) wires, which feed the rear brake/turn light elements. With the switch to the right, only the green should be live, and only the brown should be live when the switch is in the left turn position. If this isn't the case, a problem is in the switch.
Turn signals: The turn signals feed through the red wire, which draws its juice through the signal-flasher unit. To check the signal switch, connect a jumper wire to the white feed wire at the switch connector. There are four output wires for the turn-signal system, one for each corner of the car. Turn the switch to the right. The brown (right rear) and tan (right front) wires should fire a test lamp, and the green (left rear) and light green (left front) wires should be live when you turn the switch to the left. Failing this test, the switch is faulty.