Dash Turn Signal Lights Kinda Not Working?

[Mountaineerfan 44]

Background:

New circuit panel installed 2 years ago, LEDs installed in dash and tested with meter.  Rear LED sequential turn signal lights installed with electronic flasher at the same time.  High beam, instrument, brake lights all work perfectly.  New turn signal switch in steering column.

Exterior turn signals work well (front lights are slow to blink, though).

Hazards work (original relay is there)

The turn signal indicator lights in the dash will not light up.  I have noticed that when starting the car, the Brake Warning light comes on (normal) and the green turn signal lights will light briefly.

My question is why the interior turn signal lights are not coming on at all when I indicate a turn?  Would the emergency flasher relay need to be replaced with a newer electronic one?

[Kris 90]

I had to replace the turn signal flasher and the emergency flasher to get mine working properly. I believe I also had to reverse polarity on both. Don’t waste your money on the stupid adapter just use a small pick or screwdriver and remove the wires from the plug and swap their locations. I also had a led flasher I purchased that was supposed to be the correct one from CJ’s but didn’t have a ground and it wouldn’t work. I purchased 2 of these from Amazon and they worked great.

 https://www.amazon.com/CEC-Industries-EF32RL-Flasher/dp/B00JXLH7CG/ref=mp_s_a_1_3?dchild=1&keywords=CEC+Industries+EF32RL+Flasher&qid=1621458181&sr=8-3

[Mach1 Driver 560]

You must have a 70 since you state: "New turn signal switch in steering column". The 70s have a different system than the 69s and as far as I know, Ford had so much trouble with it that they stopped using the circuit after 70. It has to do with how the side marker lights are wired into the system. It becomes a big problem for LEDs. I believe Vintage LEDs was working on a system for exterior LEDs on a 70, but I'm not sure if anyone else has bothered to figure it out yet.

Just to get all the essentials clarified-

1. You have rear exterior sequential LEDs- what brand? If it isn't Vintage LEDs, then you need to find out if it is specifically designed for a 70.

2. An LED flasher, but not the emergency flasher- it should also be replaced.

3. Do you have front exterior LED turn lights?

4. How about the side marker lights- are they LED?

5. All dash lights are LEDs.

6. Do you have hood turn signals and what type? I'm not familiar enough with 70s to know if they do- I know my 69 Mach does.

7. I know this sounds ridiculous, but how about the license plate light- is it LED? All of the above lights are part of the same system, and were made to interact with one another.

I can provide 3 pages of schematics for a 70s exterior lighting system, but unless you're a Electrical or Electronics Engineer like I am, it may not help much. If your tail light system isn't designed specifically for a 70, then the easiest solution may be to convert your car to the 69 system- the side markers need to go to chassis instead of feeding back into the circuit. Its a simple enough change on a schematic, but you really need a 1970 Wire Diagram, and I only have the 69.

[Midlife 814]

Like Mach1 Driver, I agree that the wiring system for the 70 Mustang was a disaster.  Some hippy high on dope must have designed it with no one looking/checking his work. 

[Mountaineerfan 44]

14 hours ago, Mach1 Driver said:

You must have a 70 since you state: "New turn signal switch in steering column". The 70s have a different system than the 69s and as far as I know, Ford had so much trouble with it that they stopped using the circuit after 70. It has to do with how the side marker lights are wired into the system. It becomes a big problem for LEDs. I believe Vintage LEDs was working on a system for exterior LEDs on a 70, but I'm not sure if anyone else has bothered to figure it out yet.

Just to get all the essentials clarified-

1. You have rear exterior sequential LEDs- what brand? If it isn't Vintage LEDs, then you need to find out if it is specifically designed for a 70.

2. An LED flasher, but not the emergency flasher- it should also be replaced.

3. Do you have front exterior LED turn lights?

4. How about the side marker lights- are they LED?

5. All dash lights are LEDs.

6. Do you have hood turn signals and what type? I'm not familiar enough with 70s to know if they do- I know my 69 Mach does.

7. I know this sounds ridiculous, but how about the license plate light- is it LED? All of the above lights are part of the same system, and were made to interact with one another.

I can provide 3 pages of schematics for a 70s exterior lighting system, but unless you're a Electrical or Electronics Engineer like I am, it may not help much. If your tail light system isn't designed specifically for a 70, then the easiest solution may be to convert your car to the 69 system- the side markers need to go to chassis instead of feeding back into the circuit. Its a simple enough change on a schematic, but you really need a 1970 Wire Diagram, and I only have the 69.

Thanks for the response!

No, I have a 69 convertible.  I replaced the turn signal wiring in the steering column at the same time I put in the sequentials.  My front signals are bulbs (and blink slowly).  I have LEDs coming for those, along with an electronic hazard flasher relay.  Dash lights are all LEDs, and all work except for the turn indicators.  All exterior lights are bulbs EXCEPT rear sequential tails, and reverse lights.  All lights function normally.

No, I do not have hood turn signals.

[det0326 179]

I know that some led's are bipolar and some are not, could it be they are backwards?

[Mountaineerfan 44]

9 minutes ago, det0326 said:

I know that some led's are bipolar and some are not, could it be they are backwards?

I've flipped them and tested.  No luck.

[Mach1 Driver 560]

5 hours ago, Mountaineerfan said:

Thanks for the response!

No, I have a 69 convertible.  I replaced the turn signal wiring in the steering column at the same time I put in the sequentials.  My front signals are bulbs (and blink slowly).  I have LEDs coming for those, along with an electronic hazard flasher relay.  Dash lights are all LEDs, and all work except for the turn indicators.  All exterior lights are bulbs EXCEPT rear sequential tails, and reverse lights.  All lights function normally.

No, I do not have hood turn signals.

If you have a 69, then the steering column must be aftermarket (or a 70 replacement), because the ignition switch on a 69 is on the dash. All this seems to indicate that the wiring to the turn switch isn't stock either (or from a 70- yikes).

Don't go peace-meal with the lights- either do ALL LEDs or all incandescent. The flashers for incandescent lights are current sensitive, and LEDs don't pull enough amps to make them work properly. Its a combination of amps from the tail and front turn lights (on a 69) that operate the flashers. That's why LEDs require a different flasher.

Go to "How tos" on this forum and find "1969 Mustang Wire Diagram". Its too gigantic to paste in various post around the forum. On page 2-E24 and 25 you'll find the wires you are looking for. Locate detail "C" on either page. You'll see that wire #49 (that is 20 gauge) and is white with a blue stripe connects to the turn switch with #2 (18 gauge) which is the same color. #2 will go through the firewall connector to the right turn light. #49 goes up to the printed circuit and the RH dash turn light. Make sure you have a ground for your LED also. BTW, 18 gauge is larger wire that 20 gauge- its annoying how they do that isn't it?.

The LH turn is handled by wires #50(20) Green with white stripe, and #3(18) White with blue stripe. #3 goes through the firewall and to the front turn signal, while #50 goes up to the printed circuit and LH dash light. If you've got more wires than this (2 and 49, and 3 and 50), you may have the wiring for a 70, and that is a disaster.

I have noted that the colors indicated on the wire diagram don't always match the car...but that just makes it more interesting- doesn't it??

[Mountaineerfan 44]

Thanks!

The ignition switch is on the dash. 

This is the switch I replaced:

https://www.cjponyparts.com/cj-classics-turn-signal-switch-wiring-fixed-column-1969/p/TSW23/

 

[Midlife 814]

Just a reminder to everyone: do NOT replace the incandescent lamp for the alternator indicator lamp with an LED; it has to be an incandescent for the circuitry to work correctly. 

[Kris 90]

Midlife does it matter on the alternator light if you switched to a one wire alternator since the harness is no longer connected to it? 

[Midlife 814]

I don't know how a one wire alternator is used/wired for an indicator lamp.  Sorry.

[Mach1 Driver 560]

7 hours ago, Kris said:

Midlife does it matter on the alternator light if you switched to a one wire alternator since the harness is no longer connected to it? 

I'm not familiar with one wire alternators, but on the older generations (1-3) the light is used as a resistor in a circuit to start (excite) the alternator. On those cars that don't have the light, they need a resistor. Since a one wire doesn't connect to it, I don't see how it could be used, and should be disconnected...just my wild a$$ed guess.