I wouldn't doubt that the electronic flasher module died completely or lost its grounding. Try the hazards as well.
There should be a jake way to test the flasher and both circuits on the bulbs.

 

I’m going to say that unless you have something wrong with the product itself... grounding problems seem to become more prevalent when using LEDs. Check your ground on the electronic relay that you installed, as well as the ground on the tail light housings themselves. If everything works fine with your regular bulbs, I would say a grounding problem is most likely. I guess it could be the design of the products, judging from the experience of 120mm. If I might make a recommendation, there is a forum member on here by the name of gtonavy , who I have purchased all sorts of LED goodies from. They are Quality built and his service and communication excellent. ( I’m in no way affiliated with him) Good luck!

First off, this is a great forum and everyone is really helpful, responsive and knowledgeable. I appreciate that.


I now have it working by checking the grounding/contacts. I cleaned up the ground on the bulb housing, and tightened the connection on the new flasher grounding. That was it. Now the test is will it keep working. Thanks again.

 

I am having the same issue with my passenger side tail light right now. Since the running light works that means the tail light is getting its ground. I tested the brake/turn signal wire with my dvm and it is indicating at the wire. I believe that the issue is in the old socket. Looking at the 2 lead connectors it seems that they are slightly off alignment once the light bulb is locked in. That is letting the running light bulb work but it misses connection with the brake light. I tried to get the connector to turn so it would have both pins clocked right but it doesn't seem to want to turn.



Since I'm getting a new tail light wiring harness that has the tail light plug in caps I am having to get new tail light housings with the cap plug ins. My old ones have some 64 1/2 thing on them so I have to replace them with the plug in cap types anyway.



Hopefully that will end my particular problem. I would say the next step if you haven't done this is to test your brake/turn signal wire back at the tail light to make sure that it is in fact carrying voltage. If it is, your socket is also probably the cause. If you aren't getting voltage through the wire there is a problem back in the other direction somehow.

 

I am having the same issue with my passenger side tail light right now. Since the running light works that means the tail light is getting its ground. I tested the brake/turn signal wire with my dvm and it is indicating at the wire. I believe that the issue is in the old socket. Looking at the 2 lead connectors it seems that they are slightly off alignment once the light bulb is locked in. That is letting the running light bulb work but it misses connection with the brake light. I tried to get the connector to turn so it would have both pins clocked right but it doesn't seem to want to turn.



Since I'm getting a new tail light wiring harness that has the tail light plug in caps I am having to get new tail light housings with the cap plug ins. My old ones have some 64 1/2 thing on them so I have to replace them with the plug in cap types anyway.



Hopefully that will end my particular problem. I would say the next step if you haven't done this is to test your brake/turn signal wire back at the tail light to make sure that it is in fact carrying voltage. If it is, your socket is also probably the cause. If you aren't getting voltage through the wire there is a problem back in the other direction somehow.

I had this same issue on my 1965 Mustang the right side only after installing the United Pacific Sequential Tail Light set from CJPP. After nearly testing every wire, including the grounds, I found out what was causing my right turn signal to not blink. Inside spring-loaded socket, the two leads can turn 180 degrees without you noticing it, so when you install the male end of the Sequential LED lead, the incorrect leads makes contact. MY TIP: Try holding the spring-loaded in one position and if the signal doesn't blink, turn it 180 degrees the opposite direction and it will then function properly. United Pacific should have designed these sockets where they are mistake-proof and cannot be misaligned. (Maybe a square on one side of the socket and a half-moon on the other to prevent this common issue). Hope this helps!

 

Project Mustang junk strikes again.

No way are these built stout enough to live in an actually driven Mustang. Too flimsy, and too "experimental", imo.

I used their so-called warranty twice; once on each taillight.

Now, because they sent me two different versions, I have fully functioning mis-matched taillights, which look stupid. But they won't send me a matching pair, because both sides work. And look like complete crap.

Do yourself a favor, count this as a lesson learned and get something better.

 

I’m going to say that unless you have something wrong with the product itself... grounding problems seem to become more prevalent when using LEDs. Check your ground on the electronic relay that you installed, as well as the ground on the tail light housings themselves. If everything works fine with your regular bulbs, I would say a grounding problem is most likely. I guess it could be the design of the products, judging from the experience of 120mm. If I might make a recommendation, there is a forum member on here by the name of gtonavy , who I have purchased all sorts of LED goodies from. They are Quality built and his service and communication excellent. ( I’m in no way affiliated with him) Good luck!

 

If I might make a recommendation, there is a forum member on here by the name of gtonavy , who I have purchased all sorts of LED goodies from. They are Quality built and his service and communication excellent. ( I’m in no way affiliated with him) Good luck!

I've only looked at a picture of gtonavy's product, and just from the picture, you can see that they are built solid. Much more so than Project Mustang's garbage.

 

I concur! This is by far the most knowledgeable and courteous members of any forum that I have visited. Thanks all!

 

Half of vintage Mustang guys don't drive in the rain or the dark, are light bulbs not fine?

 

Neither snow nor rain nor heat nor gloom of night will stop me from driving my Mustang.

No, I am not a postman. But I like the creed. :grin2:

 

Yeah, the sequentials are cool. I think that's the right reason to get them. Usually people want to blither about visibility/safety on their Sunday cruiser, and I won't stand for it. We all know they want it because it looks cool, or their Tim the Tool Man is coming out (my lights need more power!). Which are both more valid reasons than the thin visibility/safety excuse I always hear.

 

While the coolness factor is definitely a reason to get them. I do think that safety or visibility is just as much of a reason. Stock tail lights on these cars are not very bright. In the past I was told numerous times that people couldn't see my brake lights on a sunny day. Also, most drivers these days aren't looking for it either, since they are used to third brake lights and huge tail lights like modern cars have. So, my personal thought is that in today's world of driving stock tail lights are not really adequate even in fair weather.

I've only looked at a picture of gtonavy's product, and just from the picture, you can see that they are built solid. Much more so than Project Mustang's garbage.

Those are great. I got them several months ago. They are far superior to Mustang Project's stuff or anything else I've seen so far.

 

They are able to be seen from a lot greater distance.. even in daylight hours.

 

United Pacific has broken the code on sequential taillights.

I ordered a pair (they come for sale individually, so beware) for $150 from Speedway.

They work either on Right or Left, and have a positive switch to program them. Switch to center is non-sequential, Up for Left and Down for Right.

They also have a separate wire to run if you don't want them to initially sequence when applying brakes, but I think it's cool that they do that so I left them unattached. BTW, the wires come pre-soldered and bare, so you need to insulate them to prevent shorting out in the taillight buckets.

They come sealed in bright red plastic, so they replace the entire light and red plastic assembly.

https://www.speedwaymotors.com/Unit...RCkARIsAOzRziuz6QCdPONJqhtnAYftXw4_y0tHxKTZq_1xqoCjEQCQX3CGJM9Da4AaArm1EALw_wcB

They work amazingly well, and plugs into the existing socket. Very solid, and I can't see how they will break through normal or even drastic use.

 

My GoNavy LEDs are great. Very bright and no extra wire. Easy installation. Well made. It has a switch for you to choose initial sequential or not (which applies to both brake light and blinker). Also a switch for left or right side.