K Suspension headlight relay harness

[jodawill]

I just got my headlight relay harness from K Suspension. I followed their instructions in the video to a T. The passenger side headlight is super bright now, but the driver side is worse than before.

 

I thought it was a grounding issue, so I stripped the paint around the bolts and added some dielectric grease. That didn't make a difference. I checked the resistance between the two ends of the ground wire and I found that it wasn't making a connection because it was crimped improperly. So I fixed that, but it didn't change anything.

 

Any ideas? I'm getting really frustrated here. I've been working on it for hours.

[AnotherOldJeepGuy]

If I were in your sitch I guess I'd swap the headlight bulbs just to rule out it isn't just a bad bulb.  And of course check the voltage with DMM at the bulb connector.

[Torq_Shep]

IIRC these work by taking the headlight switch input and routing that into 1 relay for low beams and another relay for high beams. Is there a brightness issue on the driver light with high beams and low beams or just on low beams? 

 

You need to check resistance of the low beam power connection at the headlight back to the relay. Likely pin 87 on the relay connector side. You should also check to make sure that you have very close to battery voltage between the low beam power light and ground on the drivers connection. 

 

 

[jodawill]

5 minutes ago, AnotherOldJeepGuy said:

If I were in your sitch I guess I'd swap the headlight bulbs just to rule out it isn't just a bad bulb.  And of course check the voltage with DMM at the bulb connector.

 

Switching bulbs is one of the first things I tried. It didn't make a difference.

 

2 minutes ago, Torq_Shep said:

IIRC these work by taking the headlight switch input and routing that into 1 relay for low beams and another relay for high beams. Is there a brightness issue on the driver light with high beams and low beams or just on low beams? 

 

You need to check resistance of the low beam power connection at the headlight back to the relay. Likely pin 87 on the relay connector side. You should also check to make sure that you have very close to battery voltage between the low beam power light and ground on the drivers connection. 

 

 

 

It affects both the high and low beams.

[Torq_Shep]

When you check the resistance between the battery ground lug and the ground pin on the drivers headlight connection, what is your reading? It should be <1 Ohm ideally. 

Checking it at the battery ensures that you are including the ground path through the screw itself as well. Did you make a new ground for this or did you use an existing location? 

[jodawill]

There's a problem with the ground wire on that side. It's not making a connection from one end to the other.

[jodawill]

I replaced the included ground wire with some speaker wire for now. I'll see if they can send me a replacement. I didn't have the right tool to crimp it, so I'm not sure how well it will hold.

[Spinnakerblue89]

On 8/14/2026 at 9:26 PM, jodawill said:

I replaced the included ground wire with some speaker wire for now. I'll see if they can send me a replacement. I didn't have the right tool to crimp it, so I'm not sure how well it will hold.

But did that help? I installed the Ksuspension headlight harness in my MJ and it left a little to be desired, but it works great nevertheless.

[jodawill]

1 minute ago, Spinnakerblue89 said:

But did that help? I installed the Ksuspension headlight harness in my MJ and it left a little to be desired, but it works great nevertheless.

 

Yeah, it made the headlights about twice as bright. But the quality of the parts leaves a lot to be desired. We'll see whether it lasts.

[Spinnakerblue89]

2 hours ago, jodawill said:

 

Yeah, it made the headlights about twice as bright. But the quality of the parts leaves a lot to be desired. We'll see whether it lasts.

FWIW, mine have been on since 2022 and I haven't had any issues. 

 

You want a really sick set up with that harness? Hook your MJ up with some IPF, Hella, or Koito glass headlamps and put some Sylvania Sylverstar Ultras inside. Your be amazed how good those look, and they ain't even LED. I've done this exact routine on four vehicles now.