Gremlins in the blinkers. And side marker lights. And...

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RC92234

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I finally got some assistance so I could do the walkaround while someone else turned the switches, and wow, I really don't know where to start. The turn signals were not self-cancelling and some bulbs were out. When my backorder of the turn signal switch finally arrived, I'm now ready to proceed and hoping I can get this worked out. I was blinking manually by flipping the turn signal lever on and off -- which turned out wasn't working at all.

Before the LED and blinker replacement, I did get a very slow and slower with each blink flashing with the right turn signal indicator in the dash and a click from the flasher unit you could hear. No, I didn't just wait to see how slow it would go. The left turn signal indicator, which had bad bulbs, did not blink; lights that worked outside lit and stayed solid, dash indicator did not.

First off, not all the bulbs were working, so replacing those was the first priority. Since I went with LEDs, I also changed the blinker unit to an electronic, extra ground-wire model. Now, no blinking at all so I just kept doing it manually until... I got a helper which revealed manual blinking was the opposite of useful, because about everything lit up, depending on which way you were turning. (Emphasis on "about") I also replaced all the lights in the dash cluster with LEDs, assuring all bulbs were polarity-correct.

A couple questions:
1) Using the new electronic flasher unit with the ground wire, is the metal frame above the glove compartment that holds all the flashers and buzzers an adequate ground?
2) Are the side marker lights supposed to act in sync with the blinkers? And the emergency flashers?

Headlight switch is new, parking lights position, turn signals and side markers all light, headlights position everything lights up. Emergency flashers work fine (if emergency flashers are supposed to also blink the side marker lights).

I made a chart to show what lights light when which switch is activated (see below). And, turn signals do not blink, no matter which way you turn but those emergency flashers? Seem to work no matter what.

- If turning left, all the correct left side things light outside, but the dash indicator does not.
- If turning right, all the correct right side things light outside, but *also*, the left side things light up at about 1/2 bright. And the dash indicator does light.

I'm boggled as to where to start. I will be replacing the turn signal gadget in the steering column, but I don't really think that's the issue, although after this exercise, maybe it is.

73 Mustang blinker lights.jpg
 
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Sorry, but I don't have a lot of time right now to go over some of your issue that I may be able to help with. Electronics is not my strong point, but on the flasher. I think the wires are crossed as they were on my car. I had the same issue at first till I figure out the factory loom was wrong. I made little jumper wires and that fixed that issue. I had to do the same for my hazards as well. As for the ground, as long as it's solid steel frame and not just a parts that may or may not be attached, you should be good. Side markers do NOT flash. As for other LED bulbs, many are polarity specific. Make sure they are correct or they don't work. Also make sure you have good grounds with CLEAN connections.
If needed, I'll get back later. Others with far more electrical knowledge will likely chime in later.
 

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I have some YouTube videos Lynda (wife) and I did re: LED light panels, flashers, etc. With the flashers cycling slowly, or not at all, you may have had just a bad bulb or a few bad bulbs, which reduced the flow of current through the oem flasher units. Those oem flashers depend on enough current passing through them, and their bi-metallic strip internally, to allow the said strip to bend and straighten out as current is passed through it, while opening and closing the circuit as the strip heats up and cools off - hence the click-click sound as the strip is bending and straightening out while the closed circuit heats up the strip, and the heated strip shuts off current flow and the strip cools off. The electronic units do not depend on current flowing through at a high enough level to heat up a bi-metallic strip, but they do need to be properly grounded.

If you are using one or more LED bulbs for the turn signal bulbs the total amount of amperage (current) is reduced to the point where often the oem flashers are not able to get their strips hot enough to operate, just like a bad bulb(s) situation.

As for where the flashers are located, and how to install and ground the electronic flashers, this video ought to help you:

If you decided to install a rear turn signal bulb with an LED turn signal panel, you will need to run a separate switch 12 volt circuit to the trunk to power the sequential flasher circuit for most such LED panels. One notable exception is the VintageLEDs.com, which has a separate logic board in its circuitry to manage the sequential flashing process. Their LED panels need to extra or special wiring. It is truly a plug and play solution. For more info check out their web sit, and look at this YouTube video:

I hope that helps. If you need any detailed turn signal and lighting wiring schematics let me know and I can provide you a snippet of the needed schematics (my snippets are too large to attach to this thread). You can email me your request for the Turn Signal Schematic snippets at [email protected]. I will get them to you via my FropBox.com site. Or, if you would like your own full schematic you can go to Forel Publishing and for a very low cost you can purchase then download a PDF of the wiring and vacuum schematics for 1973. The 1972 wiring and vacuum schematic is also very nice, but the 1973 schematic has more and better content, and the 72 & 73 wiring solutions are very similar. I find the schematics for pre-1972 Mustangs are useful, but do not have nearly as much really useful information as 72, and especially 73 Mustang schematics:
 

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The turn signals schematic is on page 6 in the 73 wiring diagram manual in the wiki section. Don't know if it will help you but if you think you have a short or wires cross it should provide the info you are looking for.
 
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RC92234, may I ask where you bought your LED's? It could be that if you bought cheapo bulbs off good ol' epay, they are not good. I learned this lesson early on when I started to convert all my lights to LED/SMD's. That's when I found Bill at HiPoParts.com and he helped solve the issues with expert knowledge and excellent parts.
On the dash turn signal indicators, you either have one bulb in backwards, a bad circuit board connection, or the wrong bulb type. It is possible that the printed circuit board is bad as well. As said, I'm no electrical expert by a long shot, but I had issues with this as well, just not as bad. My car has idiot lights, so there is ONE BULB that MUST remain an incandescent #94 at that is at the ALT position. This is critical!! (it's the only non LED bulb on my car anywhere). I suggest start with one issue, figure that our and move to the next.
I realize 73 wiring may be a lot different to the 71/72's, but in general, I think the principle is the same. Good luck, hope you get it sorted soon.
 

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As mentioned before, the turn signals and emergency flashers work via bi-metallic strips inside the flasher units. It takes a certain amount of current to make them work. The current flows through the strip to heat it up and bend it, disconnecting the circuit until the strip cools and snaps back. The amount of current is important, because the amount of heat put into the strip determines the flash rate - this is why a flasher circuit with a burned out bulb flashes faster - less current = less heat = less deflection = faster flash. Replacing incandescent bulbs with LED will either cause the flasher to go faster or not at all.

If your stock system doesn't work, there are some places to look. First, make sure all of your bulbs are working. The front and rear bulbs will have two elements - one for running lamps, one for turn signal (and brake lamp for the rears), so just turning on the lights isn't enough to check the bulbs fully. They are cheap enough I just replace them if there is a doubt, or you can cycle all of your bulbs through a working rear lamp fixture and check them with the brake lamp circuit. The older bulbs tend to plate the inside of the glass with the tungsten from the element over time, so a new bulb will be brighter.

The next step is to check your grounds. A resistive ground will limit current, cause dim light and generally cause weird problems. There are bunch black wires screwed to the car to provide ground paths that get rusty over the years. Follow the harnesses and look for these connections. Clean them up nice and shiny with your favorite sandpaper and reattach them. Don't forget to clean up the screw and the hole.

If that doesn't help, the flasher is the next easiest device to check. Again - pretty cheap, just replace it if there is doubt.

Finally, there is the switch itself. Gotta remove the steering wheel to get at it. Once exposed, it is pretty easy to see how the switch works and if there are any problems there. Cleaning contacts and cleaning out old lubricant and adding some fresh is about the only thing you can do short of replacing the mechanism. Plastic does get brittle, particularly if the car has seen a lot of extreme heating/cooling cycles, so it might be time to retire the old switch.

All of this assumes your wiring harnesses are in good shape and have not been tampered with. A visual inspection can tell you a lot - if you see any corrosion at the sockets in the trunk, those need to be cleaned up like the grounds.
 

RC92234

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Sorry, but I don't have a lot of time right now to go over some of your issue that I may be able to help with. Electronics is not my strong point, but on the flasher. I think the wires are crossed as they were on my car. I had the same issue at first till I figure out the factory loom was wrong. I made little jumper wires and that fixed that issue. I had to do the same for my hazards as well. As for the ground, as long as it's solid steel frame and not just a parts that may or may not be attached, you should be good. Side markers do NOT flash. As for other LED bulbs, many are polarity specific. Make sure they are correct or they don't work. Also make sure you have good grounds with CLEAN connections.
If needed, I'll get back later. Others with far more electrical knowledge will likely chime in later.
Thx, Geoff -- I saw that post thread where you discussed the swapped wiring from awhile back, and considered all that. But, my still original emergency flasher works just fine, and the *only* bulb that does not light is the left turn dash indicator. The others light, sometimes as the right time, sometimes not.

Per mrgmhale's video above, grounding the (new) turn signal flasher to the metal frame secured to the dash frame should be just fine. All the bulbs were tested out of the car to both determine working status and polarity. This left one I even put in what was reverse polarity; still no workie.
 

RC92234

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RC92234, may I ask where you bought your LED's? It could be that if you bought cheapo bulbs off good ol' epay, they are not good. I learned this lesson early on when I started to convert all my lights to LED/SMD's. That's when I found Bill at HiPoParts.com and he helped solve the issues with expert knowledge and excellent parts.
On the dash turn signal indicators, you either have one bulb in backwards, a bad circuit board connection, or the wrong bulb type. It is possible that the printed circuit board is bad as well. As said, I'm no electrical expert by a long shot, but I had issues with this as well, just not as bad. My car has idiot lights, so there is ONE BULB that MUST remain an incandescent #94 at that is at the ALT position. This is critical!! (it's the only non LED bulb on my car anywhere). I suggest start with one issue, figure that our and move to the next.
I realize 73 wiring may be a lot different to the 71/72's, but in general, I think the principle is the same. Good luck, hope you get it sorted soon.
Hey Stang - We've been in discussions here about LEDs before, and since then, I have converted to all HiPoParts bulbs. Also, new circuit board, and the left bulb is the same as the right bulb (and still works if tested out of the car).
 

RC92234

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As mentioned before, the turn signals and emergency flashers work via bi-metallic strips inside the flasher units. It takes a certain amount of current to make them work. The current flows through the strip to heat it up and bend it, disconnecting the circuit until the strip cools and snaps back. The amount of current is important, because the amount of heat put into the strip determines the flash rate - this is why a flasher circuit with a burned out bulb flashes faster - less current = less heat = less deflection = faster flash. Replacing incandescent bulbs with LED will either cause the flasher to go faster or not at all.

If your stock system doesn't work, there are some places to look. First, make sure all of your bulbs are working. The front and rear bulbs will have two elements - one for running lamps, one for turn signal (and brake lamp for the rears), so just turning on the lights isn't enough to check the bulbs fully. They are cheap enough I just replace them if there is a doubt, or you can cycle all of your bulbs through a working rear lamp fixture and check them with the brake lamp circuit. The older bulbs tend to plate the inside of the glass with the tungsten from the element over time, so a new bulb will be brighter.

The next step is to check your grounds. A resistive ground will limit current, cause dim light and generally cause weird problems. There are bunch black wires screwed to the car to provide ground paths that get rusty over the years. Follow the harnesses and look for these connections. Clean them up nice and shiny with your favorite sandpaper and reattach them. Don't forget to clean up the screw and the hole.

If that doesn't help, the flasher is the next easiest device to check. Again - pretty cheap, just replace it if there is doubt.

Finally, there is the switch itself. Gotta remove the steering wheel to get at it. Once exposed, it is pretty easy to see how the switch works and if there are any problems there. Cleaning contacts and cleaning out old lubricant and adding some fresh is about the only thing you can do short of replacing the mechanism. Plastic does get brittle, particularly if the car has seen a lot of extreme heating/cooling cycles, so it might be time to retire the old switch.

All of this assumes your wiring harnesses are in good shape and have not been tampered with. A visual inspection can tell you a lot - if you see any corrosion at the sockets in the trunk, those need to be cleaned up like the grounds.
Thx, Mike - All bulbs are new, and were tested out of the car to make sure they worked and determine polarity (if needed). Cluster printed circuit is also new, and I have no incandescents left anywhere in the dash. Actually, I think the only remaining incandescents on the car are the headlights. Turn signal is new, electronic and has a ground wire. Emergency flasher is old and untouched -- since it's working! lol
 

RC92234

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Thanks for all the leads! But, except for headlights, I'm 100% LEDs. I did swap out the old turn signal flasher for a new electronic version, with a ground wire. You confirmed securing it to the plate holding all the relays and flashers, etc is a valid ground. Also, emergency flasher is unchanged (original) and works fine. I'm not installing anything out of the ordinary such as sequential blinkers -- just trying to replace standard fixtures with modern bulbs.
 

RC92234

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To all who wrote, thanks... I was hoping the clue

"left side lights up when right blinker is on but not vice versa"

might inspire y'all to suggest where to start -- location of most likely culprit and maybe it would be the fix and I'd be done and not late to church (ha).

I have the manuals and an enlarged wiring diagram so I'll pick a light and trace/chase it all the way through and repeat until finished. All bulbs were tested before installation outside of the car, and in the car they all work (except left turn dash indicator), just not all are off at the right time.

But first, the new turn signal switch that I was replacing because it was no longer self-canceling.
 
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Hey Stang - We've been in discussions here about LEDs before, and since then, I have converted to all HiPoParts bulbs. Also, new circuit board, and the left bulb is the same as the right bulb (and still works if tested out of the car).
Ah, so we have. I'm just wondering if by chance there is a bad connection at the point the bulb socket inserts into the c/board. Maybe try to gently scrape the copper, there may be some contamination causing a dead circuit. Just another weird thought! By the way, do you have any hair left ?
 

RC92234

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Ah, so we have. I'm just wondering if by chance there is a bad connection at the point the bulb socket inserts into the c/board. Maybe try to gently scrape the copper, there may be some contamination causing a dead circuit. Just another weird thought! By the way, do you have any hair left ?
Ha ha! A few, but not for long at this rate: replaced the turn signal switch in the column and discovered red and green wires coming out of the brake switch that then meet up to a white/white w stripe pair just short of the center console. The profuse amount of black tape alone tells me this isn’t standard issue.
 

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Whenever you activate one bulb and another one in a different circuit comes on the culprit is usually a bad ground and the activated bulb is seeking a ground through the other bulb.

Grounds (actually lack of) are the most common reason for multiple electrical issues in these 50-year olds. Make sure the battery ground cable is run correctly from the battery to bottom screw on the voltage regulator (this provides the chassis ground) and then on to a bolt on the engine block and that all connections are to clean bare metal. Using internal star lock washers between the connector and the grounding panel really help. I would also run another ground wire from the back of the engine block to the firewall to help with grounds through old, rusted connections between the various body panels. I have positive and negative test leads that are about 25 feet long 16-gauge wire that have a large alligator clip on one end that can clamp onto the battery terminals and the other end are normal sized alligator clips. This makes it easy to run a temporary ground to a bulb that has been infected with a gremlin. If the bulb then works properly, I know it's a ground issue. I can also run a temporary hot lead to a problem bulb, and if that lights up the bulb, I know that it's a positive voltage supply problem. I also have an insulated probe that can pierce wire insulation or make contact with connectors through the back of the bulb socket. If I do use it to pierce the wire insulation, I put a dot of liquid tape over the hole to keep moisture out of the wire.

Digital volt meters don't always tell the whole story, because they don't place a load on circuits and can show battery voltage, but when there is a high resistance connection in the circuit the resultant voltage is reduced when a load is placed on it.
 
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Ha ha! A few, but not for long at this rate: replaced the turn signal switch in the column and discovered red and green wires coming out of the brake switch that then meet up to a white/white w stripe pair just short of the center console. The profuse amount of black tape alone tells me this isn’t standard issue.
Yeah, that would be "Micky Mouse" at work.
 
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Whenever you activate one bulb and another one in a different circuit comes on the culprit is usually a bad ground and the activated bulb is seeking a ground through the other bulb.

Grounds (actually lack of) are the most common reason for multiple electrical issues in these 50-year olds. Make sure the battery ground cable is run correctly from the battery to bottom screw on the voltage regulator (this provides the chassis ground) and then on to a bolt on the engine block and that all connections are to clean bare metal. Using internal star lock washers between the connector and the grounding panel really help. I would also run another ground wire from the back of the engine block to the firewall to help with grounds through old, rusted connections between the various body panels. I have positive and negative test leads that are about 25 feet long 16-gauge wire that have a large alligator clip on one end that can clamp onto the battery terminals and the other end are normal sized alligator clips. This makes it easy to run a temporary ground to a bulb that has been infected with a gremlin. If the bulb then works properly, I know it's a ground issue. I can also run a temporary hot lead to a problem bulb, and if that lights up the bulb, I know that it's a positive voltage supply problem. I also have an insulated probe that can pierce wire insulation or make contact with connectors through the back of the bulb socket. If I do use it to pierce the wire insulation, I put a dot of liquid tape over the hole to keep moisture out of the wire.

Digital volt meters don't always tell the whole story, because they don't place a load on circuits and can show battery voltage, but when there is a high resistance connection in the circuit the resultant voltage is reduced when a load is placed on it.
Don, I just knew someone with electrical knowledge would explain it in a way even I can understand. Thanks.
 

RC92234

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Progress has been made! If you count getting back to "as good as when you started" progress, that is.

Installed the turn-signal canceling contraption in the steering wheel. Two things:
1) make sure you do not overtighten the one-screw-only part that makes contact with the key cylinder. I found that with the key on and the door open, tighten it just until the key warning buzzer starts works well.
2) Spend some time massaging the wire loom that comes with the replacement device before installation. You want to manipulate the wires in the rubber sheath to spread out into a one-wire thick layer within the sheath so that you don't instead use the steering wheel supporting brackets to smash the clump of wires into the available space.

In removing the old device and wire loom, I saw three of the wires had lost insulation. I don't know that they were shorting, but that certainly opens the opportunity to ground or short if the exposed wire came into contact with the metal steering column. My exposed wires could be seen through the breaks in the sheath although if I hadn't been replacing this piece, I don't know I'd have ever seen it.

Alas, neither the exposed wires nor the turn-signal cancel thing was the problem I'm having with the blinkers. So, back to hunting shorts.
 
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Progress has been made! If you count getting back to "as good as when you started" progress, that is.

Installed the turn-signal canceling contraption in the steering wheel. Two things:
1) make sure you do not overtighten the one-screw-only part that makes contact with the key cylinder. I found that with the key on and the door open, tighten it just until the key warning buzzer starts works well.
2) Spend some time massaging the wire loom that comes with the replacement device before installation. You want to manipulate the wires in the rubber sheath to spread out into a one-wire thick layer within the sheath so that you don't instead use the steering wheel supporting brackets to smash the clump of wires into the available space.

In removing the old device and wire loom, I saw three of the wires had lost insulation. I don't know that they were shorting, but that certainly opens the opportunity to ground or short if the exposed wire came into contact with the metal steering column. My exposed wires could be seen through the breaks in the sheath although if I hadn't been replacing this piece, I don't know I'd have ever seen it.

Alas, neither the exposed wires nor the turn-signal cancel thing was the problem I'm having with the blinkers. So, back to hunting shorts.
If you're hunting shorts, are they flowery ones or do they have cars on them!! Maybe ask Midlife, he likes to "check your shorts"
Sorry, just had to lighten up the mood. Glad you're making progress.
 

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I prefer freshly laundered shorts, BTW.
 

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