Topic: Turn Signals Do Not Work

[Mark69Sportsroof]

Hi Everyone,

I'm slowly making progress on the 68 Mercury Parklane.  I have been tackling the lights.  I have all lights working except for the turn signals.  I have replaced all the bulbs, dimmer switch, voltage regulator, turn signal switch,all fuses, turn signal and emergency flashers.  Originally nothing worked when I started. 

The new turn signal switch got the emergency flashers to work but not the turn signals.

What am I missing or can check?

Thanks Mark 

[J_Speegle]

I would get a wiring diagram and a trouble or test light and start either tracing the power from the source or from the end working towards the source. Not a fun job but know of no secret if you have already checked all the connections and grounds.

[67gtasanjose]

I would get a wiring diagram and a trouble or test light and start either tracing the power from the source or from the end working towards the source. Not a fun job but know of no secret if you have already checked all the connections and grounds.

+1
Before testing ANYTHING, you may wish to confirm you have the correct amperage fuses in your TS circuit AND Flasher circuits in case any wrong wires get connected or are incorrect. Would hate to hear your efforts went up in flames.

Start at the TS Flasher unit (2-wires), one should have 12V with the key on, the other goes on directly to the TS switch. You should be able to find the same color wire at the TS switch connection. That wire will be your "12V source" to your TS wiring and is the FIRST place to confirm. The TS flasher is simply a heated element interrupter. If you jumper the two wires at the TS flasher, your 12V signal going towards the TS switch should "stay on" constantly now (as long as the key is also "on"). If it is a bad flasher for example, by jumpering the flasher, connectors together, you will remove it from the possibilities of causes to your problem AND it will provide a constant 12V source at the TS switch to aide in any further testing (if needed) If this 12V source wire is connected to the correct 12v input wire of the TS switch, the rest of the testing should go fairly easily. If this doesn't get you going, you really must have a schematic at this point. Keep in mind that some replacement TS switches have incorrect wiring colors so beware of this. In this situation, you will need to do a continuity test of the switch to determine what wire is the correct "source" wire for that switch.

[jwc66k]

Usually it's the switch in the steering column that's the problem. A wiring diagram is essential, and many service manuals have them.
Jim

[Mark69Sportsroof]

I have a new switch, service manual and wiring diagrams. Tracking and testing is next it sounds like. Thanks Mark

[Mark69Sportsroof]

Hey this may be a dumb question but does the steering wheel need to be on in order for the turn signal to work?  I don't know but thought might ground everything.  Thanks Mark

[67gtasanjose]

Hey this may be a dumb question but does the steering wheel need to be on in order for the turn signal to work?  I don't know but thought might ground everything.  Thanks Mark

No.

More likely a bad connection at the bulk connector  (at the steering column harness to the main under dash harness) or the wires are plugged into the bulk connector incorrectly (since they are often unplugged from the bulk connector to feed them down the steering column). Real easy to get one plugged in wrong, hence the concern for fused protection and the suggestion (several times now suggested) to trace out the schematics. You are literally playing with fire (or a possible short circuit of sorts) if you are not clear on this.

[Mark69Sportsroof]

Had a chance to do a few checks today.  The car isn't  at my house so I don't work on it daily.   I took picture of the old turn signal switch wires sequence and
have the same wires in the connectors slot.  Checked the t/s flasher and had 12v  on the 2 prong connector.   Thanks Mark   

[67gtasanjose]

Had a chance to do a few checks today.  The car isn't  at my house so I don't work on it daily.   I took picture of the old turn signal switch wires sequence and
have the same wires in the connectors slot.  Checked the t/s flasher and had 12v  on the 2 prong connector.   Thanks Mark

Good starting point.
1.) Be sure you are on the TS flasher NOT the hazard flasher (verified by 12V constant vs. 12V switched, it should be switched NOT constant)
2.) Identify the TS Flasher output wire COLORS (the wire of the TS flasher without that 12V switched source). Look for the same color wire at the TS column connector and test it THROUGH the connector (both sides) while the connector is plugged in. Be careful while probing so as not to distort the wiring connector pins. People often have trouble caused by the thick probe of a test light, spreading the connector and losing the connection(s).

This should verify if you are getting the 12V SWITCHED source into the TS switch or not. Once you have established this AND since you earlier said the hazards all seem to work, you should be up and running (or so I would think anyways) Electrical troubles are hard to pinpoint through a keyboard, it is really an easy job for those who understand how it all works to do it in person, but not very easy to communicate it through the written word.

Hope this gets you going.

[jwc66k]

Flashers are sometimes marked "2 lamp" or "4 lamp", the former for turn, the latter for emergency use.
Jim

[Mark69Sportsroof]

I quick update. I verified the t/s flasher and the emergency flasher.  The shop manual says emergency on right side of brake pedal and t/s on the left side of brake pedal.   Checked for power of one terminal on emergency flasher and had power. Pushed in the emergency button on steering column and had power on second terminal and the flashers come on.

The turn signal flasher showed 12v or so on both terminals.  I replaced the new t/s flasher with another one I had.  I had 12v in all 3 positions.  Right turn, neutral and left turn positions.  When I clicked it to right or left the test  light would blink and the flasher would make the turn signal clicking noise but but turn lights working. 

I know its hard to trouble shoot over the computer but your advice and knowledge really helps me.  I have identified the 2 wires from the turn signal switch and will trace them out the best I can.  Thanks Mark       

[Mark69Sportsroof]

I was wire testing with the light tester today.  I disconnected the turn signal harness from the main wiring harness it connects to.  Testing the main wiring harness the yellow wire is hot.  I figure that 's my main power line.  Then a white with red stripe wire shows about 25% power on the tester light.  Any ideal why this is?

When I touch the test light to another wire the test starts to blink like the t/s and the t/s flasher  makes the click sound.  It does it in the 2 turn positions plus the neutral (middle) position.  Again why would it do that or is that correct?


Thanks Mark

[midlife]

Yellow wire is fused hot for horn input power.  White/red wire is typically the emergency flasher input  line (4-way) to the turn signal.  It may be getting some power through the flasher can when you probe it with a test light.

BTW, test lights are not the best tools to use for electrical trouble-shooting, particularly with flasher cans and lamp sockets that have other bulbs involved in the circuitry. 

What other wire causes the turn signal to blink?

[Mark69Sportsroof]

What's the best tool to use in this process?  I'm not sure the wire, I will get back with you on that. Thanks Randy.  Mark

[midlife]

A digital volt-ohm meter that can also read DC current up to 10 or 20 amps is an excellent trouble-shooting tool, if one knows how to use it.