Another dreaded headlight issue. Symptoms a bit different.
 

Yet ANOTHER headlight issue.
This is my DD, and every night I can't drive it is costing me billable client hours. Any (good) ideas will help.
1989 XJ

Here's what I've got:

The other night I was driving in Philly, and hit a bump, but nothing really too jolting. Headlights, dash lights, and tail lights go out. Blinkers work, dash gauges work, and foot well and dome light work.

Tried the easiest route first, replaced all the fuses under the dash. Nothing.
Replaced the headlight switch. The old one was fine, so I put the old one back in, in case I can just keep using it and return the new one.

If I run a wire from the battery port on the fuse block to where the 12v+ is supposed to come in, I get it ALL back working perfectly.

I would be inclined at this point to buy a blade terminal, and run a fused wire to the switch, and replace the power wire (which currently doesn't have power) into the light switch plug.

I would assume that the problem with that is there would still be a wire between the battery and the switch that is bad? I pulled the fuse block completely out (kinda a pain in the butt), but nothing there looked fried, or even frayed. All the wires were in there tightly.

I went under the hood and tried to trace the wires back to the battery. With the header panel removed, I could see all the wires, but all looked OK.

With the symptoms being what they are, and a fused hot wire fixing the issue, what would be the next step.....I'd rather not burn an XJ to the ground with so many good parts hanging on for dear life.

Connector fried?

Sorry, no the connector is in perfect shape.

If you truly followed the +12 wire all the way back and found no breaks in the wire, the next step would be to check the continuity of that wire from where it goes into the switch to wherever it gets it's power. If there isn't continuity you probably have a break in the wire, if that's the case I would run the same gauge wire along side the harness and into the switch.

That was going to be my first move today....went out and the truck wont start, no power in the battery.

Charging now, but will also check those wires.

Appearance and function are two entirely different things. You probed the wire and there is no voltage? Cigarette lighter work?

ETA
Do you have 2 wires at the switch connector that are supposed to carry battery voltage a 10g red & a 16 g white?

UPDATE!
New multimeter arrived this morning.

Clipped the 10g wire running into the switch. Now they are 1 wire going in and 1 out.
Ran a fused power wire directly INTO the switch = Headlights work, no dash lights or tails.
Ran a fused wire from switch to the other half of the red 10g wire =

First notch = Headlights, running lights, turns, dash, tails, and brakes (EVERYTHING)
Second notch = Which should activate everything, does for a few seconds, then blows the ANTENNA 10amp fuse.

Best of luck. :clover:

Thank you, I'll post up my findings later this afternoon. Hopefully with a solution!

Pulled the fuse box apart, and there were some issues with the power antenna wire. Since I don't have one anymore, I snipped it and capped it.
Checked both ends...dead.
While in the fuse block, I took that time to clean up some of the PO's handywork. While I did that I found a few wires that didn't look good at all, so I replaced them, then replaced the fusible link out at the PDB/StartRelay with a real fuse (yeah, I know crazy right?) and POOF! Everything is good to go.

Next thing on the list, headlight harness with relay upgrade.

You'll certainly thank yourself later for that one!