96 XJ here. About a year ago I installed an aftermarket 55/100 headlight wiring harness from SMC Truck...



...and just now both my low beams went out. High beams are still working though.

I don't think it's any grounding problem at the headlights as each side is ground individually and, like before, the highs still work.

Where should I begin testing?

I assume the fuse is still good, and that maybe the problem is at one of the two relays. Both relays are a 1" cubed black box with writing...

SHORI
S11-1A-C1-12VDC
30A/12VDC
COIL:12VDC

Is there a way to test the relay maybe? I have a multimeter but not enough knowledge to just jump into this.

Thanks

 

Try the high beams relay on your low beams. Replacement relay is BWD 4136 if you need one.

 

Correct me if wrong, but isnt it four total relays now?
Two original to stock harness and then the two in the Putco harness?

If so, then check both. Also, most relays are super easy to check with a multimeter and a couple bits of wire.

 

The reason for the Putco or any other aftermarket headlight harness is to provide relays for the headlights. There are none in the factory harness.

 

I have the harness too. So that explains why the wires were so damned small in the first place. Cheapskates lmao

 

Yep. Per the factory harness all power goes through the headlight switch. It robs voltage from the headlights and hence the poor lighting. Also that switch can burn out. Had one guy post that he was cruising down the interstate after dark when he lost all lights.

 

That's exactly what happened to me too...doin freakin 70 mph down a dark interstate and the headlights go out. They only did that on high though. Researched the problem for years and nobody had an answer. All that stopped though once I added this aftermarket harness.

Just saw one of the relays has some of the writing worn off, the identifying line that I think should read S11-1A-C1-12VDC. So I'm not sure if both relays are the same now. I'll swap their positions anyhow and see what happens.

 

Most likely your low beam relay died. It looks like the harness has plug connection to the relays. If you swap the plugs to the opposite relays, and you get low beams and no high beams, you have a bad relay. If you swap and nothing changes, you likely have no voltage for your low beams coming from your dimmer switch. You should hope it's a relay. It will be the easiest and cheapest to fix.

 

They're the same.

Number one cause of relay failure is poor grounds. "Looking" at the grounds accomplishes nothing.

Undo each one, remove paint at the attaching point and reinstall with OxGard on the connection.

Secondly, many folks get lazy and don't fasten the relays down.
So, they rattle around under the hood.

Thirdly, if the relays are not mounted in the proper orientation, they get moisture in them.

 

Switched them relays and yep now the lows don't come on...so looks like problem solved.

Thanks for the pic there. That's exactly what mine look like.

 

GLAD you got her fixed and THANKS for letting us know.