I replaced my headlights last night with H4 conversions, in part because I thought one of them was dying. My passenger side headlight is fully bright, but my driver side headlight is dim. But the H4 conversion didn't help -- the dim issue remained (though not much worse).

For diagnostics, I unplugged the passenger side light and plugged in only the driver side, and the driver side was fully bright. So, I'm assuming that there's something preventing the driver side from getting full power when both headlights are plugged in and turned on.

Also, this is a relatively recent issue. It has cropped up in the past few weeks.

I have considered getting the 4Crawler wiring harness, but in this case I would like to know how to diagnose the root issue before replacing those parts.

Any advice? Is it a bad ground, cut in the wire, etc?

 

could always add an extra ground to see if that is the issue..

 

What is your voltage at the headlight plug?

I am quite certain that the 4Crawler harness will fix it as it totally replaces the power wiring to the headlight, only using the factory wiring to throw the relay.

 

You need to check the voltage at the light with both headlights connected. Sounds like a short in the wiring. Could be a bad ground as indicated by the other poster.

Tell us your voltage, that will help a lot with where to start.

 

Thanks for the responses. I didn't get a chance to do this tonight because I was putting another coat of paint on my truck. But, something weird happened.

So, I turned on the truck and the driver light was dim at first. Then I drove around for a few minutes and it magically brightened up to maximum brightness.

Does this change the diagnosis? I will try and check it out tomorrow.

 

loose wiring? or maybe a little corosion on a contact in the relay?

 

Won't help as it is the headlight switch on the steering column that supplies the ground connection that turns on the headlight. Check the voltage and find out where the drop is coming from and go from there:
- http://www.4crawler.com/4x4/CheapTri...ml#VoltageTest

 

Bad connection in the fusebox. There are separate fuses for the right and left headlights, and if one is out/bad the system backfeeds and one light burns dim.

 

Good to know! Most of the dim headlights I have ran into are usually a bad ground but I have not had a problem with any on my Toyota's yet.

 

Brilliant. This proved to be the cause. One of the connectors in the fuse box was loose, and when I wobbled the fuse around, the lights went to full brightness immediately.

Thanks as well to everyone else who provided suggestions. I think I will still check the voltage to the headlight plugs just in case. And 4Crawler, I might end up getting your harness after all.

 

On the subject of 4Crawler's harness.

He has the switched power harness in stock and a module to convert it to switched ground.

He does not have the switched ground harness in stock, which is the "correct" one to use on our rigs. I'm not saying that the other won't work, but the system in our rigs is switched ground.

I have e-mailed back and forth with Roger. He has minimum buy concerns versus selling the things in a reasonable period of time. Very valid concerns. If there is enough interest, maybe we can get a run of the parts. How do we go about doing a group buy survey on Yotatech? I'm not the most web savy guy around.

Thanks,

Mike

 

yeah mine was because i didint have all my grounds hooked up