My goal for this upgrade was to safely add 55w lights to the back of the jeep that are operated by both a dash mounted switch and by shifting the transmission into reverse. I had one blank in my factory switch panel, so I chose to use a factory fog light switch to make the install as clean as possible.
12ga ring terminals
20ga ring terminals
12ga female disconnect terminals
20ga female disconnect terminals
20ga wire taps
12ga inline fuse holder
12v 30A relay
1 factory fog light switch for a 1999 TJ
18-22ga non insulated butt connectors
55w fog lights (H3)
3’ of ¾” angle aluminum
Self tapping sheet metal screws
Key ring Swiss Army Knife
Assorted nut/screw drivers
1999 TJ FSM
2004 TJ FSM
Step One: Disconnect the negative battery cable
1. Remove the trim piece from the top of the dash.
2. Remove the two screws that go from the radio bezel into the dash. (early TJ’s have a third screw behind the ashtray)
3. Remove the radio bezel by pulling out.
4. Remove the four screws that hold the switch panel to the dash.
5. Carefully pull the panel away from the dash.
6. Remove the blank by prying up on the retaining tabs on the top & bottom of the panel. (I found that a pick with a 90 degree bend worked well)
A 1999 TJ fog light switch has four pins.
Pin 1=dimmer signal
Pin 2=switch output
Pin 3=12v in
I thought about buying a pigtail for the switch, but they seem to be ridiculously expensive, so I had to come up with another way of connecting the switch. I ended up using 18-22ga non insulated butt connectors to connect 20ga wire to each pin on the switch. I slightly crushed the pin end of the butt connector because the inside diameter of the connectors is a little too large to snugly hold the pin. After altering one end of the connectors to fit the pin, I crimped 20ga wire into the other end and used heat shrink tubing on all the connectors.
Reverse circuit tie-in:
In order for these lights to work as intended I needed to find a wire that puts out 12v when the jeep is in reverse. I could have spliced into the harness near the reverse switch on the transmission or in the monster connector behind the dash on the driver’s side. As luck would have it, jeeps with the compass/temp mirror make finding this circuit simple, as one of the wires in the mirror harness (which is on the dash just under the trim piece) carries the signal from the reverse switch. I tapped this wire and ran a 20ga wire to the wire which connects the switch and the relay. I put a diode in this wire to isolate the signal of the dash mounted switch from the reverse circuit.
Main power wires for lights:
I used 12ga wire to power and ground the lights. I put an inline fuse holder about three inches from the positive terminal of the battery, and then ran the wire across to the driver’s side of the firewall and then through the rubber grommet above the gas pedal. After getting through the firewall I routed the wire to the cavity behind the switch panel (where I put the relay). From the relay I ran the wire along the bottom of the dash (where the glove box hinges) to the side of the tub and then back to the passenger rear corner of the tub.
I used a piece of aluminum angle attached to the stock tire carrier to mount the lights. I look at this as a temporary mounting as I hope to move these lights to a future tire carrier. I put the aluminum as close to the tailgate as possible and then bent it until it “looked right” and mounted the lights at each end.
1. Switch pin 1 20ga to O/D harness panel dimmer
2. Switch pin 2 20ga to relay pin 86
3. Switch pin 3 20ga to fused 12v
4. Switch pin 4 20ga to ground
5. Relay pin 86 20ga to Switch pin 2
6. Relay pin 85 20ga to ground
7. Relay pin 30/51 12ga to Battery (fused)
8. Relay pin 87 12ga to + side of lights
9. +side of lights 12ga to Relay pin 87
10. -side of lights 12ga to ground
11. reverse circuit wire 20ga to connection #2 wire
In the end this setup works exactly as I hoped it would. The lights mirror the function of the factory backup lights, and can be turned on with the dash mounted switch.