LED Brake/Blinker Bulbs Kills Blinkers??

l008com

Well-Known Member
#1
I bought a set (4) of 3157-CK bulbs from superbrightleds.com... Their lumen values were really high, so on paper these should have been a very good replacement for stock bulbs, AND they are only $10 per bulbs.

So I installed them tonight. Their dim mode looks like it's completely on par with the incandescent's dim mode. Their bright mode looks like it's not as bright. I haven't decided if I want to keep them or not, I haven't had to make that choice, because somehow they kill my blinkers!

So with all four of these red 3157's installed: Whenever my tail lights are on, the blinkers/hazards do not work. And inside on the dash, the blinker indicators (green arrows) remain dimly lit all the time.

Turn off the tail lights and the blinkers work normally.

They are not CAN bus bulbs as far as I can tell (see for yourself), and I am even using an LED compatible electronic flasher in place of the factory flasher.

My dash with my tail lights on, and my blinkers and flashers off:


I emailed SBL but I'm sure they're just going to tell me to return them. I figured I'd post the problem here too in case there's some other known issue that is causing this? I was so excited to FINALLY have good working red 3157's.
 
#2
:undecided: What happens if you pull the front 194 bulbs from the corners, do your rear turns still act up and the cluster stay lit? It sounds like the parking lights are back feeding into the turn signals.
 
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l008com

l008com

Well-Known Member
#3
I'll have to try that another day, I've already put everything back together.
The 194's and the 3157's in the front are all LED already, FYI.

How would this 'backfeeding' happen?
 
#4
:wink: I know, I had a similar issue when I put LED 194 bulbs in.

Edit: The 194 bulbs don't have a dedicated ground, the parking light and turn signal use each other as a ground. Due to the lower resistance of the LED, a little bit of current leaks through the entire system, and is enough to light up the other bulbs.

If you flip the 194 bulbs around, the problem will change. When you activate the turn signal on one side, the parking light on the other will flash along with it.
 
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l008com

l008com

Well-Known Member
#5
So is there a solution to this problem? I'm still not understanding what's causing it but I've never read that it's "impossible" go to all LED on TB exterior lights. So there must be SOME solution to this, yeah?
 
#6
There is, essentially you have to add your own dedicated ground, making it a 3 connection circuit instead of just 2. Before places sold switchback modules, I had to design my own, so that's one step you can leap frog.

You'll either have to splice into your stock wiring for this, or buy expensive connectors to go between the 194 harness and the 194 bulb holder in the corners. So you're either spending time, or a decent bit of money, to get this mod done and behaving properly.
 

gpking

Well-Known Member
#7
Hold on, all 4 of the bulbs are CK 3157's?
Only the brake/tail socket (and the front turn socket) are CK. The rear turn signal sockets are non-CK. That is probably your issue.
The only time I had weird behavior like that is when I put non-CK bulbs in the CK sockets (and vise versa).

I'm all LED with no issues.

Also, you should install a resistor on the tail circuit or you might lose cruise control.

You should only need to add a ground to the front 194 sockets if you replace them with LED. Mine caused backfeeding.
 
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l008com

l008com

Well-Known Member
#8
There is, essentially you have to add your own dedicated ground, making it a 3 connection circuit instead of just 2. Before places sold switchback modules, I had to design my own, so that's one step you can leap frog.

You'll either have to splice into your stock wiring for this, or buy expensive connectors to go between the 194 harness and the 194 bulb holder in the corners. So you're either spending time, or a decent bit of money, to get this mod done and behaving properly.
So grounding the 194's is all I need to do? That's not too bad. As a test, removing those little 194's should also (temporarily) solve the problem too then right? I still haven't decided if I want to keep these red 3157's so I'd like to test them more before I'll have time to get around to the 194 wiring mod.

Hold on, all of 4 the bulbs are CK 3157's?
Only the brake/tail socket (and the front turn socket) are CK. The rear turn signal sockets are non-CK. That is probably your issue.
The only time I had weird behavior like that is when I put non-CK bulbs in the CK sockets (and vise versa).

I'm all LED with no issues.

Also, you should install a resistor on the tail circuit or you might lose cruise control.

You should only need to add a ground to the front 194 sockets if you replace them with LED. Mine caused backfeeding.
Yeah all 4 of my reds are CK, and my front ambers are non-CK. Mine's a 2008.
I replaced the 194's with LEDs very early on but only have issues with this when I put LEDs in the rear, oddly enough. With regular bulbs in the rear, the front LEDs work totally normally. *shrug*
 
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#9
Please use the multi quote feature when replying to multiple posts, to avoid double posting :popo:

MultiQuote.jpg
 

Matt

Silver Supporter
#11
There is, essentially you have to add your own dedicated ground, making it a 3 connection circuit instead of just 2. Before places sold switchback modules, I had to design my own, so that's one step you can leap frog.

You'll either have to splice into your stock wiring for this, or buy expensive connectors to go between the 194 harness and the 194 bulb holder in the corners. So you're either spending time, or a decent bit of money, to get this mod done and behaving properly.
@Blckshdw Can you throw me a bone on how to do this? I'm getting sick of looking at my indicator lights on the dash illuminating when the lights are on.
 
#12
@Blckshdw Can you throw me a bone on how to do this? I'm getting sick of looking at my indicator lights on the dash illuminating when the lights are on.
Quickest and easiest method would be to buy a pair of ready-made switchback modules. I believe prices on those have come down considerably from when they first came on the scene. You'll have 3 connections on the input side (park, turn and ground) and 2 on the output side (park and turn). I used the fender grounds for mine.

All you'll need to do is either splice into your wiring, or get some connectors/pigtails to make an extension piece. The first time I did the 194 mod, I bought the Delphi connectors. Pricey... This second time I bought some empty 194 bulb bases to plug into the factory socket, ran those inputs to the module and bought some 194 socket pigtails that could twist lock into our headlights (slight mod with a razor blade was needed)

That's pretty much it. Just have to determine what components you want to use.
 
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l008com

l008com

Well-Known Member
#15
So does anyone have maybe a drawing or something of exactly what you need to do here. This thread is old and the red LEDs have actually been sitting in a box on the floor in my truck for years now. The textual description of this mod doesn't do it for me, I just don't understand it. But I would like to do it.

I also don't know if I ever got around to pulling my 194's and trying the red's again, I should give that a shot at some point.
 
#16
I didn't make a sketch of the one I made. THe link I used, that had the schematic is gone. But if you do a google images search for "type 2 switchback schematic" you'll see a number of ways to do this mod. Just have to pick one that looks like a comfortable match for your skill set
 
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l008com

l008com

Well-Known Member
#17
Is a simpler solution to this problem to simply snip the 194s, and splice them into the 3157's in parallel. Then they would blink in sync, instead of alternating, but it would remove the 194's from the picture?
 
#18
Well the problem with that is the 3157 is a 3 connection circuit, and the 194 is a 2 connection circuit, so you can't make a simple connection like that. I found my old photoshop file, so maybe this will help...

Using a DPDT relay, you can make a polarity changer, which is what you need for the 194 bulbs, since whichever color is not being used, its + contact becomes the ground for the color that's active. So you'd use 3 diodes to prevent back feeding. Pins 11 and 8 would be connected together, as well as to the parking light contact of the 194 bulb. Pins 6 and 9 connected in the same fashion to the turn signal contact of the bulb. That covers your outputs.

For the inputs, the parking light signal from the truck goes to pin 13. That makes pin 11 hot, and sends the signal out to the parking light contact of your bulb. Pin 6 is treated as ground for the bulb, which is why pin 4 is connected to (fender) ground. This would be your normal state.

The turn signal from the truck comes in at pin 16, which activates the relay and flops both of the armatures, changing the polarity of your circuit. The diode from pin 16 to 13 will make sure the bulb gets power, in case it's daytime and your parking lights aren't on. So power will go through pin 9, to the turn signal side of the bulb, and pin 8 is the ground, exiting at pin 4. The diodes coming off pins 1 and 4, make sure your turn signal doesn't back feed through the parking light and cause the other side to flash in sync. At this point, you'll have the old Type 1 switchback, where the colors will alternate. :suicide:
I'm not entirely sure how to make it a Type 2 from here. I know you'd want to have a capacitor across the relay coil, to keep it engaged on the turn signal mode, but not sure exactly how to interrupt the parking light signal, so you'd actually get the flashing...


194 Switchback Polarity Module.jpg
 
#20
:undecided: I had to go back and read all the old posts... A simpler option would be to snip the parking light wire feeding the front 194 bulbs, and taping off the truck side pieces. Extend the bulb side pieces to the fender ground. This effectively makes your 194s turn signal only, and gets rid of the back feeding issue. Would that work for you?
 

gpking

Well-Known Member
#21
So what you're telling me is, either LED tail lights or LED 194s, take my pick.
Yes, unless you want to add some additional wiring.
... snip the parking light wire feeding the front 194 bulbs, and taping off the truck side pieces. Extend the bulb side pieces to the fender ground. This effectively makes your 194s turn signal only, and gets rid of the back feeding issue.
Or...

What I did to solve this and retain both functions is to introduce a diode module on each side from a "towing diode kit" at about $5 a piece depending on where you find them.
https://www.amazon.com/dp/B0002Q81Y4/?tag=elightbars-20

The original park and turn signal wires get connected to the "IN", the "OUT" runs to the anode side of the LED, then I added a ground wire between the fender and the cathode side of the LED.
The diode prevents backfeeding and essentially ORs the inputs.
t10diode.jpg

So they operate as turn signal during the day, and illuminate solid at night.
 
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l008com

l008com

Well-Known Member
#22
That's seems simple enough. Although I clicked your link and they were $25 each not $5 each :/

Also, just to be doubly clear, all the LEDs act totally normally once those are installed, one on each of the front 194 side marker lights?
 

gpking

Well-Known Member
#23
That's seems simple enough. Although I clicked your link and they were $25 each not $5 each :/
That link is to a 4-pack. Only 2 are needed but I couldn't find less than 4 unfortunately.

Also, just to be doubly clear, all the LEDs act totally normally once those are installed, one on each of the front 194 side marker lights?
Well, assuming your lights worked normally before LED, yes. The diodes just stop the backfeeding between park and turn signal circuits which seems to be your only issue.
You can see that problem illustrated in the video I posted a while back with my left signal backfeeding to the right one:

If you've already remedied hyperflash and made sure you used the correct CK/non-CK bulbs, fixing the 194s is the only other issue. I think we covered all bases in this thread.
 
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l008com

l008com

Well-Known Member
#24
That link is to a 4-pack. Only 2 are needed but I couldn't find less than 4 unfortunately.


Well, assuming your lights worked normally before LED, yes. The diodes just stop the backfeeding between park and turn signal circuits which seems to be your only issue.
You can see that problem illustrated in the video I posted a while back with my left signal backfeeding to the right one:

If you've already remedied hyperflash and made sure you used the correct CK/non-CK bulbs, fixing the 194s is the only other issue. I think we covered all bases in this thread.
Cool cool cool. Ok one last question, about those diode boxes. Once they're installed and looking more or less like the picture you took, how do you finish it off? I need it to be water resistant and not likely to unplug itself from vibration. Should I just go nuts and wrap the whole thing with tons of duct tape? Or something else?
 
#25
With the female spade connectors, they should fit pretty tight out of the box. If you want, you can take some pliers or vice grips, and give them a pinch to make them grab a bit tighter on the module's tabs. Just don't pinch em too hard, or you won't be able to insert the tabs in the first place :laugh:

You really shouldn't be seeing much water behind your headlight with normal road driving, but if you're really concerned, wrapping them in electrical tape won't hurt anything.
 
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l008com

l008com

Well-Known Member
#26
When doing this kind of thing, do you guys solder the connectors on to the wires or just crimp them on?
Also if doing a lot of similar mods, do you ground each one individually to whatever is nearby, or do you connect all the grounds and do one big ground?

I just checked the Diode link above and in addition to all the $23 3rd party sellers, amazon had a set of 4 for only $13.55. Now that's a dealio! Ordered that and a soldering iron for $40. I really need to learn to do at least basic soldering for spliced connections.
 
#27
If you're connecting modules together, like this, using crimp connectors is fine. As for grounds, I look to use factory grounds if one is nearby.
 

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