I changed the wire harnesses a few years ago with high temp harnesses because I planned on putting the headlights on relays but never got around to it.

I noticed a while back that every now and then the driver headlight would seem to get brighter while driving and I never put much thought into it.

I realized last week that the left headlight was dim. I wiggled the harness and the light went bright and dim with movement so I changed the harness. The new harness gives me a dim light but no bright light, if I move it just right then the bulb goes out. I changed the bulb and it has the same issues.

Tonight I checked out the fuses and the left headlight fuse was blown. I swapped it out and with the new fuse in there I get two dim headlights. With no fuse in the left headlight slot I have the bright passenger light and a dim driver light.
I thought there was one fuse for both headlights and I didn't check the fuses first since the right light operates like it should.

Does anyone know what is going on? I'm thinking a bad ground for the left headlight but I'm not sure.

 

In my experience, 99% of electrical issues begin with a bad ground. That would be the thing I checked first!

 

Do you know where it is grounded at? The wiring diagram shows the red/orange wire going to the multifunction switch. Violet going to the fuse in the PDC. Violet/white going to Joint connector #1 in the PDC, is that the ground? I haven't been back out to the truck yet so I don't know if the ground wire on the socket is violet/white but what I really need to know is where the other end of that wire is at.

 

I am not sure, I have not looked into it that much for the headlights. Though I will be doing it soon for the tail lights. Someone else will hopefully chime in here.

 

Dodge had to be different, and the switch actually provides ground path. Check all your connections are clean, and tight. If wiggling the connector makes the light do the bright/dim thing, you found your problem.

Why they are both dim with a good fuse installed is a good one. That is just bizarre.

 

Would it be possible to take that ground and splice into it? Just ground it to the frame or metal or yada? Or is the ground required to go back to the switch?

 

Ground is somewhere in the cab, I think.... Better bet would be to rewire the headlights, so the switch only controls relays, and the relays actually supply power to the lights. I think someone even makes a plug-in harness for just such an occasion. Can't recall who it was though.

 

Would that possibly be Daniel Stern lighting?

 

There is a write up on this on page 4 of the DIY section, but, the pics aren't there any more...... LMC truck sells a complete harness that is supposedly plug and play.

 

I knew about the one on lmctruck and I was wanting to get that one but just haven't gotten around to it yet. I have a reason to now.

I thought the socket was the issue also but It does it with the old and the new bulbs and sockets so two sockets and two bulbs, that's what has me scratching my head. It goes out when I rotate the socket a little bit. When i rotate the good lights socket a little bit it will go a tiny bit dimmer than usual then back to bright. Maybe those Dorman high temp headlight sockets are just garbage.