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Converting 3157 Tail Lights to LED

11K views 56 replies 10 participants last post by  Irv 
#1 ·
Hey guys, I've had great luck using the Sylvania Zevo led bulbs you can get at local auto parts stores for around $25.

It uses different leds for the low and the high so you get great contrast, just like factory. It also fires backwards into the reflector so you get a nice even light distribution just like factory.

I installed them on my motorcycle and they are great. They come on super fast. But when I installed them on my T bird, the cruise control doesn't work. I swapped to an electronic flasher, but that doesn't have any effect as far as making the cruise control work again.

If I have one bulb incandescent and one led, the cruise works, but if both are led, it doesnt.

It's very strange.

Has anyone had this issue before?
 
#3 ·
Yes, and it's for the same reason why the tail lights on most LEDs are lit up when the power is on (dimly!) ... the cruise control uses the incandescents to pull the input down, and there's not enough current on your Zevo's to do that. (On most LEDs, there's enough current flow; but there's also enough to start the LEDs to, well, emitting light.)

A load resistor will do that; you don't even have to go the 6 ohm route.

IIRC, about a 570 ohm 1 watt resistor on either side does the job just fine. And doesn't get anywhere near as hot (for bulletproof, use 570 ohm 5 watt sandohms and bolt them to the body somewhere ... )

(I need to do that to my Cougar to get the LEDs out when the power's on but the lights are off ... )

RwP
 
#5 ·
Well this thread has definitely made me decide to stick to incandescent taillight / turn signals. I did the interior all LED including the dash and the Reverse bulbs which all was a worthwhile improvement.

Using a load resistor has always been a such big negative . IMO the best reason to switch to LED is the lower power consumption.
 
#6 ·
Your not making sense. Did you read the above where you can run a 570 ohm resistor as opposed to a 6 ohm? It's barely any load at all.

I'm gonna experiment with some small loads on just one side and see what it takes to get it working. I might even just add a weak 1 or 2 watt tiny bulb to the wires. I don't know if it's the running wires or the brake wires that need a little load.

The led zevo bulbs are worth it. It's a bit brighter than stock on the brake circuit, plus the immediate on and off really grabs your attention. It should help people see your brakes and rear signal better.

Here's a video of my bike with led on left and incandescent on the right. Look at the speed difference when I apply the brake. The incandescent takes much longer to come to full brightness.

https://youtu.be/HXzbD58GihE
 
#7 ·
Umm ... it's the brake lights.

See, it's the fact that they're connected to the cruise control electronics so that, with incandescents, it holds that line close to ground; when you step on the brake pedal, it goes to 12V or so and says "Whoa! No cruise!"

With the LEDs, there's not enough current to pull it down properly; all we need is to pull it down far enough, which doesn't take a full "load resistor" of 6 ohms.

RwP
 
#10 ·
So cruise control uses both switches, plus it monitors the load across the tail light bulbs? It seems a bit odd.

I think I have a 194 bulb and socket laying around. Maybe I'll try wiring it into the circuit and see what happens. Hopefully we need the small load on the brake/bright circuit so my little 194 bulb will only come on with the brakes. Seems simple enough.
 
#13 ·
Well, the input to the cruise control electronic box is either a logical "OFF" or a logical "ON" for the brake lights. And no, that's not in the manual; but since I've been tickling electrons since the 60s and work on computers for a living (at the repair level), I tend to think in the terms of a logic device.

The EVTM is the Electrical Vacuum Troubleshooting Manual; if you're working on your car's electrical without one, IMO, you're about like those apes at the start of 2001:A Space Odyssey and just beating on things with clubs and grunting *grins*

The Center High Mount Stop Light, or CHMSL, is that light up on the package tray in the back.

RwP
 
#15 ·
There are two switches on the brake pedal; on NO (normally open) one NC normally closed.

If either change, the system disengages.

The BOO switch goes to the brake lights; the special thing about the center brake light is that it doesn't go thru the MFS (Blinker switch).

I'm not sure anything else is on the other switch at all, thus the need for a load.

A 570 w resistor only needs to be 1W to be at a 2x safety factor; 5W s 10x. :)

These are 560 ohm, and have mounting flanges for $3.




This is a flame proof design, $0.64ea.



:)
 
#17 ·
I finally got it all working. I didn't want to order parts online, so I took a single 194 bulb and socket I had and used some splices to tap into the ground wire and brake wire (black and yellow wires).

Out of curiosity, adding the bulb to the running light wire had no effect, it's the brighter brake wire that you need a little load on. So now I have a little 194 light in the trunk that comes on with the brakes. No big deal. Lol

BTW, without that little extra load I noticed that the bright, brake led glowed a little when the running lights were on. With the 194 plugged in, it went out.

I also found out that the Zevo bulbs are polarity sensitive. I plugged in both and none were working. I freaked a little thinking I had fried them. Then I tried flipping them 180° and bam, all good again. :)
 
#22 ·
A few reasons on top of the fast turn on/off:

-Uniform flash front and rear from the side view

-With hyperflash disabled in the flasher I won't know, at least not right away, when the front incandescent bulbs burn out.

-The amber color of the standard bulb reflects off the housing/lens even when off, which somewhat defeats the look of clear/euro corners.
 
#23 · (Edited)
Did any of you have issues with the Zevo bulbs creating a black hole (illumination cold spot) in the center of the taillight housing? I noticed that with mine and decided to return them because that look was too distracting. The black hole expanded and contracted with the low LED on and the high LED blinking, and the two sides were also uneven with the driver's side black hole being more prominent than the passenger side.

I ended up going with Morimoto X-VF bulbs instead and got better results.
 
#27 ·
Heh, too damn much. Actually, I think I paid about $40 a pair when I got them on sale over July 4th weekend, so it was a little cheaper than usual.

I first tried the Zevo which I returned, then tried out the ACME RedRocket, but despite directing light similarly to the X-VF, the RedRockets lit up the corner taillight housings unevenly and were actually too bright, especially next to the Thunderbird's LED taillight panels. If you weren't paying attention to the CHMSL illumination, the low LEDs in the RedRockets made it look like you were always stepping on your brakes. The X-VF was pricey, but I thought it looked better than everything else I tried in those corner tails.
 
#26 ·
As an update, with the added 194 bulb on the drivers side I've noticed that if the cruise control is on and I activate my left signal it turns the cruise off. It's mildly annoying, but it seems you should add a small load to both left and right side brake bulbs. Not just one side like I have.
 
#28 ·
Yes, to both; or to the BOO switch output.

RwP
 
#29 · (Edited)
I had been running Morimoto X-VF LED bulbs in the corners until one of them quit working recently. That was a blessing in disguise because ever since learning and coming to the conclusion that the X-VF bulbs are awful in our reflector housings, I was looking for an excuse to dump them especially since the warranty on them ran out. I said good things about them two years ago, but I know better now.

When it comes to replacing incandescent bulbs with LEDs on a blinker circuit, I think most people are aware of the hyperflash issue, but once you get past that, beam pattern is still a major consideration that gets overlooked. I already had a terrible experience with the X-VF switchbacks up front, but with the X-VF red, the entire bottom half of the housing was a hot spot. Prior to my decklid taillight upgrade, if you weren’t noticing my CHMSL, it looked like I was riding the brake at night. It wasn't as bad as the TRS Acme RedRockets, but still very noticeable.

I tested three different pairs of red LED 3157 bulbs from Amazon and the pair that I kept are short tower-style bulbs with the same length and similar uniform light distribution as the stock incandescents, but brighter and quicker to illuminate.

Much like how we've learned to not stuff plug-and-play HIDs in reflector headlight housings, the same principles apply to the rear corners. Don’t go for the brightest LED bulb, even though everywhere you browse on Amazon, many automotive LED bulbs boast inflated lumen ratings in the product title. What you really want is a good contrast between high and low signals as well as a beam pattern that works well in our fluted reflector corner taillight housings.


Height comparison between incandescent 3457, Amazenar 3157, and Morimoto X-VF 3157


Top of the bulbs showing how the Morimoto produces a prominent hot spot because of the top heatsink and lens, and the length doesn't help by putting the light closer to the lens of the taillight housing


Morimoto X-VF on the left vs. Amazenar on the right, off the brake; notice how the Morimoto is much brighter even in the bumper reflection


On the brake, they look similar, but the Amazenar has much better light distribution even though it's not as evident in the photo

Here is the link to the Amazenar bulbs, but the bulb style is more important than the brand since they're all marketed under different brands and these links are subject to change all the time on Amazon.
https://www.amazon.com/gp/product/B01NA9KJ8F/
 
#30 ·
What you really want is a good contrast between high and low signals
Yes, the stock bulbs have about a 10 to 1 ratio of wattage between the 2 elements. A lot of bulbs look like the brakes are always on and you can't tell when they actually do come on or blink. Leds just can't go very dim without special PWM circuitry which no one uses in car bulbs. Zevo's are good in this regard because they use 2 different leds. A smaller dim one and a bigger brighter one.
 
#34 ·
Unfortunately that was my only copy, I made it on the fly on my phone and tinypic gave me no notification the images would be lost.


I would disregard it though, it slowed down hyperflash but still blinked faster than normal for some reason, at a rate right between normal and full hyperflash. There might be two stages to it in these, it works in other vehicles(which is where I learned of it) I just ended up using load resistors in parallel with a stock unmodified flasher instead, works fine.
 
#36 ·
The flasher operates basically like a relay and relays make a buzz sound if the voltage is out of their operating range. What are your lights doing when the noise is happening? Are they full on, or dim, or flickering or just blinking normally(besides hyperflash)?


Off/on topic what’s the best parking light 3157s these days? I still have ZEVOs but they’re not near as bright as the red ones are
 
#44 ·
Actually, it's worse than that.

A tungsten filament in the 3157 is about4 ohms cold, so it draws even more current.
 
#46 ·
The standard flasher is a bi-metallic strip flasher.


It flashes proportional to the load.

The led capable one is a timer circuit and a relay.
 
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