LED lights and the 97+ XJ

First lets start out with explaining what a LED is and how it works.
A Light Emitting Diode is essentually a diode that emits light when an electrical current is passed through it. Diodes have an Anode, and a Cathode. They only allow electricity to pass in one direction. Which is why if you wire one up backwards you have no voltage through it hence no light. Voltage to the Anode produces a output voltage on the cathode. Reverse the polarity and you get nothing. That's the reason why when you install one backwards it doesn't work

The issue you guys are having with converting to LED is in the front wiring harness with the way the OEM wired the side marker lights. They are grounded through the #2 Turnsignal lamps filament (which is why when that lamp burns out you loose the sidmarker lamp, and the sidemarker turnsignal). You can use a standard SPDT relay to essentially drive the side marker with the only difference being that the side markers with flash in unison with the front lamps always instead of only when the parking lamps are off.

You will need to cut the wiring to the side marker. (I'm using the FSM for my 99, but I would think it's safe to assume that all 97+ use the same colors on the front end light harness.)

Left side
Brown is your Parking light
Lite Green is the Turn Signal
Connect the relay as follows.

Brown from the harness to the Common or #30
Brown from the side marker lamp socket to the NC or #87a
Green from the harness to the coil #86
Green from the side marker lamp socket to a ground
Ground terminal #85 on the relay.
Finely insulate the #87 terminal on the relay to prevent shorting out.

Right side
Dark Green / Yellow is your Parking light
Tan is the Turn Signal
Connect the relay as follows.

Dark Green / Yellow from the harness to the Common or #30
Dark Green / Yellow from the side marker lamp socket to the NC or #87a
Tan from the harness to the coil #86
Tan from the side marker lamp socket to a ground
Ground terminal #85 on the relay.
Finely insulate the #87 terminal on the relay to prevent shorting out.

Ideally I would make an attempt to locate the relay in a location where it is protected from direct sprays of water, and to seal all you wiring splices to keep moisture out.

Note you will still need to use a electronic turnsignal/hazard flasher unless you want the speed flash.

If you are replacing your stock bulbs in the taillights with LEDs you shouldn't need to do anything to the wiring. If you are replacing your taillight with boxes that use only one light for the parking, stop, and turn you can use a trailer light driver.

Nice posting - that will help those late model XJ's with exactly where to land the wiring.

scoobyxj said:

First lets start out with explaining what a LED is and how it works.
A Light Emitting Diode is essentually a diode that emits light when an electrical current is passed through it. Diodes have an Anode, and a Cathode.

They only allow electricity to pass in one direction. Which is why if you wire one up backwards you have no voltage through it hence no light. Voltage to the Anode produces a output voltage on the cathode. Reverse the polarity and you get nothing. That's the reason why when you install one backwards it doesn't work

The issue you guys are having with converting to LED is in the front wiring harness with the way the OEM wired the side marker lights. They are grounded through the #2 Turnsignal lamps filament (which is why when that lamp burns out you loose the sidmarker lamp, and the sidemarker turnsignal). You can use a standard SPDT relay to essentially drive the side marker with the only difference being that the side markers with flash in unison with the front lamps always instead of only when the parking lamps are off.

You will need to cut the wiring to the side marker. (I'm using the FSM for my 99, but I would think it's safe to assume that all 97+ use the same colors on the front end light harness.)

Left side
Brown is your Parking light
Lite Green is the Turn Signal
Connect the relay as follows.

Brown from the harness to the Common or #30
Brown from the side marker lamp socket to the NC or #87a
Green from the harness to the coil #86
Green from the side marker lamp socket to a ground
Ground terminal #85 on the relay.
Finely insulate the #87 terminal on the relay to prevent shorting out.

Right side
Dark Green / Yellow is your Parking light
Tan is the Turn Signal
Connect the relay as follows.

Dark Green / Yellow from the harness to the Common or #30
Dark Green / Yellow from the side marker lamp socket to the NC or #87a
Tan from the harness to the coil #86
Tan from the side marker lamp socket to a ground
Ground terminal #85 on the relay.
Finely insulate the #87 terminal on the relay to prevent shorting out.

Ideally I would make an attempt to locate the relay in a location where it is protected from direct sprays of water, and to seal all you wiring splices to keep moisture out.

Note you will still need to use a electronic turnsignal/hazard flasher unless you want the speed flash.

If you are replacing your stock bulbs in the taillights with LEDs you shouldn't need to do anything to the wiring. If you are replacing your taillight with boxes that use only one light for the parking, stop, and turn you can use a trailer light driver.

Click to expand...

After drawing this out on paper I'm withdrawing this layout. I realized that unless you have the parking lights on you would not have a side marker turnsignal. I'm currently working out a solution that should work. Give me a day or so to iron out the new circuit.

My revised post on LED turn signals.






First lets start out with explaining what a LED is and how it works.
A Light Emitting Diode is essentually a diode that emits light when an electrical current is passed through it. Diodes have an Anode, and a Cathode. They only allow electricity to pass in one direction. Like a one way street for electricity. Which is why if you wire one up backwards you have no voltage through it hence no light. Voltage to the Anode produces an output = voltage on the cathode. Reverse the polarity and you get nothing. That's the reason why when you install one backwards it doesn't work

The issue you guys are having with converting to LED is in the front wiring harness with the way the OEM wired the side marker lights. They are grounded through the #2 Turnsignal lamps filament (which is why when that lamp burns out you loose the sidmarker lamp, and the sidemarker turnsignal). If you are handy with wiring and have a basic understanding of electronics you can use a standard SPDT relay a pair of diodes, a resistor and a capacitor to essentially drive the side marker with the only difference being that the side markers with flash in unison with the front lamps always instead of only when the parking lamps are off. Also if you can use a trailer light converter to drive them using only the STOP lamp, and turn signal inputs to drive the lamps. You would connect the brake lamp input to the parking circuit, and turn to turn on their respective sides. You will not use the parking lamp input on the controller.

You will need to cut the wiring to the side marker. (I'm using the FSM for my 99, but I would think it's safe to assume that all 97+ use the same colors on the front end light harness.)

Left side
Brown is your Parking light
Lite Green is the Turn Signal



Right side
Dark Green / Yellow is your Parking light
Tan is the Turn Signal



Ignore the specs on the diodes in the diagram, and just use a 1N4007. As far as the CAP goes use a 16v or higher, and 10K uf. You May need to experiment with the cap if you have issues with the relay not staying energized long enough during the turn signal cycle. You can lengthen the time the relay stays energized by increasing the uf rating of the cap. Remember diodes only work one way they have to be installed correctly or this circuit won't work. Also where is shows the diode across the coil of the relay. The diode can just be grounded with the resistor and cap. You can also buy spike suppression relays with the diode built in. Once you cut the wires for the sidemarker you will connect one wire to the relay, the other will be grounded paying no attention to the color of the wire other than to get the ground side of the lamp socket to the cathode of the LED.


Ideally I would make an attempt to locate the relay in a location where it is protected from direct sprays of water, and to seal all you wiring splices to keep moisture out.

Note you will still need to use a electronic turnsignal/hazard flasher unless you want the speed flash.

If you are replacing your stock bulbs in the taillights with LEDs you shouldn't need to do anything to the wiring. If you are replacing your taillight with boxes that use only one light for the parking, stop, and turn you can use a trailer light driver.

Scooby.

thanks for the tutorial, it helps lots. However, how do you explain the working of everything like it should except when it seems to act up if its been cold the previous night or in the morning

2001XJ said:

Scooby.

thanks for the tutorial, it helps lots. However, how do you explain the working of everything like it should except when it seems to act up if its been cold the previous night or in the morning

Click to expand...

Don't really know. Maybe it has something to do with the design perimeters of the LED lamps or you have a second issue that's coincidental.