Trouble shooting light problems

Alright, my dash illumination and tail lights don't work.

I have headlights, hi-beams, fog lights, dome light, turn signals, hazards, brake lights, and back-up lights.

My gauge cluster is new to the Jeep...came off another '85 XJ (full guages on this one). The headlight switch is also new.

Where do I start? How do I troubleshoot?

TIA.

Ok I am having the same problem on my 1990 XJ. First check the fuses. Check the Park Fuse I believe it is a 10amp. Then check the Instrument Panel Lamp Fuse I know this one is a 5amp fuse. Then check the voltage to the battery side of the instrument panel lamp fuse while turning the dimmer; If it is zero then it is OK if not then replace the headlamp switch. Finally test the ohms on the ground side of the Inst. Lamp Fuse with the lamps off; If it is almost zero then it is fine if it is not then repair the ground. The 12volt supply wire is shorted to ground from the fuse. Replacing the fuses fixes mine for about ten minutes and I havent been able to test the others yet; will do tonight or tommorrow. Hope this helps. If you figure it out let me know how you did it because I really want to get mine fixed too.

Just went thru this with my MJ. The panel backlights are wired into the taillight circuit (but have seperate fuses, so check both of them like Dan said). The brainy engineers did this as a safety-check feature...if you loose your taillights your dash goes out to let you know, since you can't see that they're not working. Check the ground lug for the rear lights for looseness/corrosion and you'll probably find the problem. Not sure where that location is on an XJ, but MJ's ground to a lug under the bed in the rear.
My problem, however, ended up being a loose connection at the back of the fusebox for the dash fuse, that I didn't find until one night when it was dark out and I could see little blue flashes (arcing) coming from behind the panel.
HTH,
Jeff

Good info Jeff...thanks!

I looked through the FSM and the Chiltons manual that I have for my XJ and there is no mention of a ground lug for the tail lights.

Can anyone steer me in the right direction as to the location of that lug? I'm going to go work on it after work this afternoon.

Like Dan1990XJ said the parklamp fuse is a 10A. Check for battey power at this fuse also. If these check out fine then I would look at the headlamp switch. Sometimes the connector will melt at the switch due to a poor connection over time. If you get to the headlamp switch power should come in on the Red/blue wire and switched output should be on the Dark blue wire. If you have power in and no power out when the switch is on then the switch/connection is bad.

Just had a similar problem in my 96 XJ Country. Some jack ass broke into my rig and took off with $2500.00 worth of stuff. The yanked out the stereo created electrical problems under the dash and with the signals. The mechanic called me and said insurance would not pay for some of the problems because they were not related to the break in. Although I had no problems with any of the lights until after the break in he was convinced it was something else. I authorized him to diagnose the trouble on my nickel and he found about two gallons of water inside the left rear fender well. It was trapped between the outer shell and inner wall. This area had several relays that were under water and VERY fried. He drained the water and replaced the relays and now all works fine. All this just happened at the same time as the break in so I swore it would be related but wasn't. This affected my running lights, turn signals and emergency flashers. He also found a blown fuse in the under hood fuse box. $495.00 later my XJ is on the road again. The relays can be reached by removing the left rear interior panel where the stock spare mounts up.