Troubleshooting Sequential Turn Signals

This article covers troubleshooting 1967-1968 Mercury Cougar sequential turn signals. While most the information as been acquired through experience on a 1968 model, the ideas can be applied when servicing a 1967 model too. This information is also applicable to 1967-1969 T-Birds as they share the same basic design and parts.

The turn signal system has five electro-mechanical parts: the turn signal switch, (located in the steering column), a turn signal relay (located under the dash), a directional relay, an emergency relay, and a motor-driven sequencer (located in the driver's side trunk under the mat or behind the backseat in T-Birds). The 1967 system also has an emergency relay and a turn indicator relay under the dash. The most failure prone parts are the mechanical sequencer, the turn signal switch, and the emergency relay in the trunk. Circuit diagrams may be found in the appropriate year factory shop manual.

Basically, the system works as follows: when the directional lever on the turn signal switch is moved, it completes circuits that select and feed power to the corresponding bank of lights. Power for the lights is fed through the turn signal relay to the sequencer. The sequencer has three cams that, when rotated, depress switches corresponding to the inboard, center, and outboard tail lights. The power is then routed first through the emergency relay (which disconnects all but the center light if the emergency switch is on for Cougars and connects all lights together for T-Birds.) and then to the directional relay. This two-sectioned (right and left) relay routes power through to the selected bank of lights. Since brake lights are not sequenced, the directional relay allows all lights to turn on simultaneously when the brake light power feed is energized. But when the turn signal switch is actuated, the brake light power feed is disconnected and the turn signal feed is activated to allow the directional signal to override the brake lights.

Now that you understand a little about how your turn signal system works, you can start troubleshooting. You will need a VOM (Volt-Ohm-Meter) and the circuit diagram for your year car. The most common complaints are: no turn signals, one or more lights on but not flashing, one or more lights flashing, and center and front lights only flashing. The first place to check is the in-line fuse under the dash to the right the steering column. The next stop is to check all bulbs and their sockets. If these are all good, then now the real sleuthing must begin!

No turn signals:

When the turn signal lever is depressed, no lights come on anywhere. Start by depressing the emergency switch, if the emergency flashers work, the turn signal switch is most likely bad. Next, listen to the directional relay for a click while moving the turn signal lever. If there is no sound, disconnect the turn signal switch from the harness and check it according to Table 1. The table shows wire pairs that should be shorted together when the switch is in the position indicated. If any of the connections are open, replace the switch. Usually the switch has failed when the plastic around the riveted contacts in the area around the emergency button appears to be burnt or melted. This can be seen with the steering wheel removed. For more information, review the Turn Signal Switch Diagnosis Guide

Some or all lights on but not flashing:

This usually means that the motor in the sequencer has quit. Remove the white cover from the sequencer and see if the motor is turning the cam. FORD has discontinued the unit but an electronic replacement is available.

One or more lights flashing:

If all bulbs are OK, the trouble is most likely in the sequencer. The switch contacts erode away with age. Sometimes they can be cleaned up with an ignition points file, but this is just a temporary fix. The best solution is to replace the sequencer with an electronic unit.

Center and front light flashing only:

This is the normal mode for the emergency lights on a Cougar, but will occur if the emergency relay fails. On a T-Bird with the emergency flashers on, this indicates that the emergency relay is bad.

Dash indicator light doesn't flash:

The indicator relay is calibrated to click and operate the dash light when all four bulbs (1 in front, and 3 in back) are working - check the bulbs first. A low battery, poor charging system, bad connections in the turn signal switch, or bad relay can cause this problem




Green, Orange-Blue Blue, Green-White Blue, Orange-Blue
Green, Green-Orange Blue, Green-Orange Blue, White-Blue
Blue, Red Blue, Red Blue, Red
  Green, Orange-Blue Green, Green-Orange

Table 1. 1967 or 1968 Turn signal switch connections

1967/1968 Turn signal switch connector pin diagrams


1967 Cougar

1968 Cougar

Turn indicator relay (4-pin) C7WY-13A366-B N/A
Turn signal relay (3-pin) C7WY-13A366-B C8WY-13A366-A
Directional relay C7WY-13A366-A C8SZ-13A366-A
Emergency relay (under dash) C7WY-10B926-B N/A
Emergency relay (in trunk) C7WY-10B926-A C7WY-10B926-A
Stop lamp relay (early) C7SZ-13482-B N/A
Sequencer (flasher) C7SZ-13350-C C7SZ-13350-C
Turn signal switch (w/o tilt) C7ZZ-13341-F C8SZ-13341-A
Turn signal switch (w/tilt) C7ZZ-13341-E C8SZ-13341-B

Table 2a. OEM Parts list

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1967 Cougar

1968 Cougar

Electronic sequential system: replaces sequencer, directional relay,emergency relay, and stop light relay. C7WY-13A366-AS (early) C7WY-13A366-BS (late) C8WY-13A366-AS
Electronic sequencer CE-1 CE-1
Directional relay C7WY-13A366-AR C8SZ-13A366-AR
Stop light relay C7SZ-13482-BR N/A

Table 3. Replacement Parts list

04/22/15 SEQTS

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