Using LEDs in the front fender side-markers on a Jeep Wrangler TJ

Steel City 06

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Installing LED headlights, taillights, and front turn signals requires nothing more than replacing your flasher relay in the steering column with an LED flasher relay.

However, to use LEDs in the front fender side-markers, you'll run into issues. The side-markers ground through the unused filament on the front fender bulbs, and if the resistance is too high in the front fender bulbs, as is with a light emitting diode, the side-markers will not light, and the front LEDs May light inappropriately.

In order to get LEDs in both, you need to convert the fender flare sockets into a 3-wire setup using standard diodes and dimming resistors.

It can also be done with load resistors, but load resistors will waste energy and are more finicky

Here is a crappy guide to a 3-wire setup:

27A89AF7-E1CD-4D9B-8780-70B108233159.jpeg


Buy a set of 1 watt resistors and fine tune the low brightness using the resistor. You want a brightness that is bright enough yet contrasts with the high brightness for the turn signal. I think I used 350 ohm resistors in mine.

It will simply alternate low/high brightness when the turn signals and parking lights are on, and low when only parking lights are on.

No changes are needed to the front fender sockets if this wiring is followed for the fender flare sidemarkers.
 
Guess I better provide something better than a half-baked answer to a generic thread...

Anyways the reason you can't just stick LEDs in your front fender and sidemarkers is because the sidemarkers are grounded through the fender filaments. When the running lights are active, the current flows through the small sidemarker filament and through the big turn signal filament in the fender. The fender filament doesn't get hot enough to emit significant light, so it remains dark. When you turn on the signals, that formerly grounded line becomes hot, turning on the signals and turning off the sidemarkers at alternating intervals.
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If you just shove LEDs in the front fenders, this becomes an issue. The LEDs don't pass enough current to allow the sidemarkers to light, and the sidemarkers pass too much current causing the front fender LEDs to light inappropriately.

So the goal is to bypass the floating ground by making your own 3-wire turn signal. In order to do this, you simply cut the wires leading to the sidemarker, and splice in a few things.

Note these splices occur in the SIDEMARKER, and not the front turn signal. Don't molest your front fender turn signal wires. They work fine on their own.

First step is to ground one side of the harness. This gives the current somewhere to flow to that is unimpeded and does not cause errant lighting issues elsewhere.

Second step is to splice in a pair of diodes. These diodes are here to prevent backfeeding of the opposing circuit. Otherwise your turn signals would light up your running lights, and your running lights would light up your turn signals. These diodes act just like check valves in a piping system to prevent current from flowing backwards. They MUST be installed in the correct orientation.

3rd is to determine which wire is the running light wire, and splice in an inline resistor to reduce the current flowing through the LED and effectively dim the bulb. The wire can easily be determined by looking up the wiring diagram in the FSM. Alternatively, you can test the wires with a voltmeter.

For your resistor, you want to find whichever one gives you your optimal low brightness. Take the socket pigtail, stick in an LED, and touch it to the car battery terminals. This is your full brightness, or the brightness you will see when you use turn signals or hazards.

Next, play around with a 1 watt resistor kit to find which one gives the optimal low brightness. You want to go as bright as you can while still having a crystal clear distinction between low and high brightness. Mine ended up being in the range of 350 ohms. Take this resistor and splice it onto the diode from the running lights. (The order of resistor/diode is not important.)

Next, you need to do the 3 way splice. Splice the ends of the diodes/resistor lines together, and to your non-grounded wire on the pigtail. Ground the other wire if you haven't already.

Turn on the signals and check for normal operation. Turn on the running lights and check for normal operation. If the LED doesn't light, try flipping it 180 degrees.

Congratulations! You are now fully LED. If you also switch out your taillights and all the bulbs in the dash and instrument cluster, you can get your running light amperage draw below 0.3 amps. This means you could leave your parking lights on for up to THREE FULL DAYS without fully killing your battery. I can personally attest they will last overnight without killing a battery.

Note that this process permanently commits you to using an LED in the sidemarker. You can either use an LED or halogen bulb in all other locations.

You could also use a halogen bulb in the sidemarker in an emergency, but note that it will not light with the running lamps because the inline resistor is blocking the current. The turn signal should work for a short period of time, though it may burn out more quickly.
 
I'll keep this in mind should I decide to go back to LEDs on mine. I recently put it all back stock trying to sort out a multifunction switch issue.
 
You wouldnt happen to have the part # for your flasher relay?
I can't remember. I purchased one from ebay and another from Amazon. One was junk and didn't work right and the other is fine. When I get the time I'll crack open the steering column and take a peek.
 
Nope. This is just a way to make your own 3-wire LEDs using the existing socket and housing.

(Just need to make sure whatever 3-wire kit you buy can't backfeed anything)
 
Rather than cut the wires to the side marker light I made a patch cable that will do the same thing. Way more easier to build the circuit, no cutting of wires, and it's reversible.

When the adapter is installed you may run into the following issues.
If the LED does not light at all, you need to spin the bulb 180 degrees in the socket.
If the LED does light but it is bright, you need to rotate the plug into the factory socket by 180 degrees.

The second if statement has to do with the default mode of the side marker is dim, and when it flashes it gets bright. If you put the plug into the factory socket the wrong way the bulb will always be bright, even when it flashes.

If you want to build this circuit like I did here's the parts you will need the following additional items to your BOM.

194 Male Sockets
https://www.amazon.com/gp/product/B07WTZMNZL/?tag=wranglerorg-20

194 Female Sockets
https://www.amazon.com/gp/product/B07H8F322J/?tag=wranglerorg-20

Here's what it looks like. I haven't tested it yet but I did build the circuit exactly Steel City 06 described.
20200613_113113.jpg
 
Question concerning LED’s......
I put LED side marker lights in my tube fenders before reading this post. (Also have LED headlights, taillights, and front facing running lights.)
All lights lit up like they should, but turn signals didn’t work (even with new LED relay) and turn signal indicator on dash lit up as if they were burnt out. Also found out that my LED brake lights are now not working, but taillights are
I unhooked side marker lights hoping this would fix everything, but same problems.
Any advice? Specifically my brake light issue? Thanks
 
Question concerning LED’s......
I put LED side marker lights in my tube fenders before reading this post. (Also have LED headlights, taillights, and front facing running lights.)
All lights lit up like they should, but turn signals didn’t work (even with new LED relay) and turn signal indicator on dash lit up as if they were burnt out. Also found out that my LED brake lights are now not working, but taillights are
I unhooked side marker lights hoping this would fix everything, but same problems.
Any advice? Specifically my brake light issue? Thanks
It's probably due to the LEDs in the front running lights/turn signals. Switch those for non-LED or rewire your side markers. I had the same issue when I installed rear LEDs, so I just swapped the front signals back to non-LEDs until I get around to rewiring.
 
I “unwired” the side marker lights and taped the ends up and still same problem. Are you saying to wire back up incandescent bulbs?
Are your side markers led bulbs 3 wire or 2 wire? If they are 3 wire, it should work. If they are two wire, you need to follow the directions above to get your lights to work properly, or put incandescent bulbs back into the front turn signal markers.
 
They are 2 wire. Front are 3 wire. Front wiring from Jeep is 3 wire, and side is 2 wire. Are you saying incandescents in front facing parking lights? Or just side marker lights?
Sorry for the questions, just sick of messing with all this
 
They are 2 wire. Front are 3 wire. Front wiring from Jeep is 3 wire, and side is 2 wire. Are you saying incandescents in front facing parking lights? Or just side marker lights?
Sorry for the questions, just sick of messing with all this
I am saying incandescent in the front facing parking lights. If you want LEDs in that spot, you need to rewire the side markers to be 3 wire. It has to do with the floating ground that is used with the factory wiring. The floating ground does not work with LEDs.