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You replaced the 1157 bulbs with LEDs, but what? As I'm sure you are aware the 1157 has two incandescent filaments that share a common ground.
Do you know if the 1157 replacement LEDs are bidirectional? This is really two (or more) LEDs that are in parallel but with their polarity reversed so it doesn't matter how they are installed. I can't see why they would be since they are probably in a bayonet style package. You could test for that by connecting 12vdc one way and then reverse the polarity. If it lights in both directions then it is bidirectional. That could begin to explain the screwy operation.

Or...I suppose one or more of the LEDs could have a high reverse current- can you measure mA in both directions?
 

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Discussion Starter #22
You replaced the 1157 bulbs with LEDs, but what? As I'm sure you are aware the 1157 has two incandescent filaments that share a common ground.
Do you know if the 1157 replacement LEDs are bidirectional? This is really two (or more) LEDs that are in parallel but with their polarity reversed so it doesn't matter how they are installed. I can't see why they would be since they are probably in a bayonet style package. You could test for that by connecting 12vdc one way and then reverse the polarity. If it lights in both directions then it is bidirectional. That could begin to explain the screwy operation.

Or...I suppose one or more of the LEDs could have a high reverse current- can you measure mA in both directions?
Bidirectional they are not (just checked it). I even tried putting + to one "filament" and - to the other (not using the case ground at all) and it just ever so slightly lit a few LED's, but it was barely noticeable. Now the strange observation... I get 0.25A when + is on the bright terminal "filament" and - is on the low "filament", and the bulb base starts to get warm. The LED bulb has a resistor on the low and a diode on the high, I wonder if it needs another diode in series with the resistor or is that a purpose built feature? The bulbs I have pull 0.10A on low and 0.30A on high (my taillight LED's pull 0.85A on high and 0.30A on low, but these are very bright and I'm not having issues with those). Hmmm... might be worth a try to install diode's on the low filament... what do you think?
 

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What are your voltmeter readings? Make a chart for all 6 wires for the front sockets with lights on then T/S on left then right bulbs out. Then install the led's and test again. An error will have to show if there is a wiring/switch issue.
 

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The 30 ohm resistors are dropping resistors to set the voltage at a safe level for the LEDs. The 120 ohm resistors are in parallel with the LEDs, shouldn't do anything, but would pull .08A each.

Inserting a diode as you suggested (lets assume it is inserted in the RF Park circuit) would prevent the back flow to the LF Park, but it would also prevent the RF Park from operating under normal conditions.

Any time I try to insert a schematic or picture on this forum I find that I've exceeded the kb limit. It would be much easier to exchange information via email or another forum like 69Stang, or Stangfix. PM me if you want to pursue some other method of communication. BTW, both of those forums have a full car 69 schematic on them (don't confuse it with a wiring diagram). The classics are similar enough to see how most things should work. The park/turn/brake circuits intermingle and make for a difficult diagnosis.

Can I assume that you have a meter that will read mA?
 

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I tried like the dickens to get LED front directional and side markers to work when installed on my 1970 Mach 1. I finally gave up. Back to incandescent and no problems. Seems 70’s are a problem.
I have a solution to the problems with the 1970s. The issue is the side markers are tied to the park lights. I came up with an isolated side marker bulb. With this you can run LEDs.

1970

Gary
 

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I have a solution to the problems with the 1970s. The issue is the side markers are tied to the park lights. I came up with an isolated side marker bulb. With this you can run LEDs.

1970

Gary
Interesting, so will it behave like a 70, or like a 69? That is, will the side markers still flash alternately with the turn signals?
 

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What year mustang is this? The 1970 mustang parking / directional signal lighting is unique for only one year. If the headlights or parking lights are on, then the LED marker lights on that side will flash alternately with the turn signals. If the headlights or parking lights are off, then the LED marker lights on that side will flash in unison with the turn signals. 69 mustang side markers don't blink.
OP any response on what car you are working on?
 

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Gary, I’d like to order your 70 LED parking/turn signal kit since you came up with the solution side bulbs. Do they come with the kit, and is it just a simple plug in for the side markers?
 

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Gary, I’d like to order your 70 LED parking/turn signal kit since you came up with the solution side bulbs. Do they come with the kit, and is it just a simple plug in for the side markers?
The Park and Side markers are separate.
The new side marker is a wedge light with an additional ground wire.

Just shoot me an e-mail at:
[email protected]

Gary
 

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Discussion Starter #34
OP any response on what car you are working on?
Alan, its a 66.

Dave

I have some experience with LED and old mustangs. Why don't you PM me and we can have a call to discuss your issues?

Thank you

Gary
Gary, I appreciate the offer to hash this out privately but I'd like to make the information and my attempts (both failed and successful, hopefully) available for all to enjoy. That and every time I have time to think about it its already past 10pm and I wouldn't feel right calling somebody that late (I know I wouldn't like it)!
 

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Discussion Starter #35
Another quick update with nearly a complete fix...

So, I yanked both bulbs out tonight, took them apart, and soldered in a diode before the main resistor to ensure electricity only flows one way. Slapped them both back in and clicked on the blinkers... left blinker on, only left bulb blinked, hooray! Right blinker on, both lights blinked...WTF?! Long story short, one of the diodes I soldered in was bad (what are the odds?!?!). Swapped it out and now only the directed bulb blinks when commanded, hooray! But, I don't think I am all the way out of the woods yet.

With the headlights on, I'm not sure its doing everything correct (hopefully somebody can confirm correct light function). With headlights on, taillights are on, front running lights are off. I then click the left blinker on and it blinks from high to low brightness (vs high to off as would be expected). The dash turn signal indicator bulb does the same thing; high to low brightness vs on and off. I don't know what to look at for this issue, so suggestions are welcome.

Almost there!
 

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First part is correct - not sure what you are saying with high/low? Is this for the front directionals? If so, seems like something is crossed - should brighter with LED's all the time - no dimming.

Maybe Gary has the answer - he's the man when it comes to LED problems - help me out for sure.
 

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Discussion Starter #37 (Edited)
Hooray<img src="http://forums.vintage-mustang.com/images/smilies/alert.gif" border="0" alt="" title="alert" class="inlineimg" /> Success<img src="http://forums.vintage-mustang.com/images/smilies/alert.gif" border="0" alt="" title="alert" class="inlineimg" />

After checking my new headlight switch, it’s wiring, the LED flasher, and a few more odds and ends the light bulb finally went off... what about the rear LED bulbs (I think somebody may have mentioned it on this thread)? They work fine and are doing what they need to do, but what if they are affecting the fronts? Turns out, they were!

I pulled both rear bulbs out and everything on the front worked fine! Crap, I wonder if the rears are backfeeding the fronts... after a rear bulb tear down sure enough they were. I needed to install a diode on the bright “filament” side to keep voltage from the running light circuit lighting up the bright side but at the running light reduced voltage (how LED’s change the brightness level on dual filament bulbs).

I definitely chased my tail more than once, but dammit, I figured it out! So anyone installing LED’s throughout their classic is going to need to either find a bulb manufacturer that sells bulbs with diodes already installed (good luck confirming that unless it’s a company who actually assembles the bulbs themselves, Gary/gtonavy?) or you will have to install them yourself.

I have attached two pics of the before and after modification of the bulbs I was working with. Ignore the cooked resistor 😮😉. While I had the headlight switch out I also did a simple mod that keeps the front running lights on when the headlights are switched on. It looks nice with the added lights up front.

Whew, glad that’s over!
 

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