Awhile back I purchased LMC's heavy duty headlight harness and installed it. I've been very happy with how much brighter it has made my headlights. One negative though is that my daytime running lights are now full high beams. Normally, the drls are high beams with less power I believe. Any thoughts on how to adjust the wiring to return the drl's to their normal power while keeping the benefits of the harness upgrade?

 

glad you are not behind me.

are you allowed to disable your drls?

 

you're not supposed to disable them and I'd rather keep them. Right now I just drive with my low beams on so they're not as obnoxious.

 

the high beams are on at lower power for some drl others use low beam at low power.

something sounds not right on you installation.

have you asked lmc for guidance?

 

I'm guessing the LMC kit bypasses the stock headlight wiring which provides power to the headlights for both regular and DRL use, and that's why everything is full brightness now.

 

The stock harness routes power to the headlights through the switch. The LMC harness powers the lights right from the battery, leaving the switch to just turn power on and off.

 

sounds like that is the problem.

and you say you are having problems with the turn signal and wipers.

somehow the harness is the problem.

 

You'd think so, but the turn signal wiper issue has been there since I bought the truck. This DRL issue is a direct result on using the harness upgrade. I believe that the harness wasn't designed for drl equiped vehicals.

I'll try and take some pics of it tomorrow. I'm hoping that I need to reconnect one of the wires from the original harness.

 

The DRL module modulates the voltage to the high beams. The low voltage is enough to turn on the headlight relays, which feed full battery voltage to the headlights. There's no way to modulate a relay, so you'll either have to bypass the relays for the high beams or go without the DRLs (if that's legal, I have no idea). You should be able to run the relays on the low beams even if you have to reconnect the original wiring to the high beams.

 

The fix I believe is to cut the wires coming out of the dimmer switch on the floor and use them to trigger the relays...

By using the harness as it is you will always have the DRL's triggering the high beems...

The DRL's are powered from another source other than the headlights them selves but power the headlight high beem circuit... so by isolating the relays from DRL's (cuting the wires at the dimmer) you can have the relay trigger wires you need to use with out the DRL's interfearing... headlight relays work, and DRL's work.

I can't say this is the same for your truck... and I have yet to install relays for my headlights... but after talking too some people here at FTE and where I live I believe it is the way to do it.

Now there might be another way to fix the problem but it requires you too use a diode... A properly installed diode (a one way valve for electricity) should fix the problem.... the problem I had was I don't know much about them...

 

Or you can unplug you DRL's...I guess...lol

 

I have some serious lights on my truck, and many of them have automatic operation - for instance I converted the factory low beams to DRLs, I also added a delayed-exit module that keeps them lit up for a minute after engine has been shut off, and I also have them wired in with the e-brake pedal so DRLs shut off when the e-brake is applied - it's amazing really what you can achieve with some relays, diodes, and resistors. I'm saying this because I think the same approach can be used for your factory DRL malfunction issue - as already stated the LMC relay harness will provide full battery voltage to your headlights no matter how low the relay trigger voltage is (well, as long as it ain't so low where it won't trigger the relay), however you can add your own circuit to the LMS harness that can feed proper DRL voltage to the high beams. You'd have to source another SPST (4 poles, normally-open) relay and some wiring and terminals for it, then you have to find a way to drop the battery voltage down to DRL specs before you feed it into the relay - I'm thinking a nice power resistor could be used for that. Then you take the relay output and splice it in with the high-beam power feed from the LMC harness - this way the high beams will get either full battery voltage through the LMC harness, or reduced DRL voltage through your add-on harness. To trigger the new relay you have two choices:
a) locate the output feed wire from the factory DRL module or headlights switch or whatever it is that provides the reduced voltage and run it to your new DRL relay, or
b) find a key-on wire in the engine bay and run that up to the DRL relay resulting in DRLs being always active as long as engine is running.
Approach b) will necessitate in the install of a second relay (of the 5-pole SPDT normally-closed type) for the DRLs to shut down the first relay whenever the high beams are engaged with the main headlights switch, and of course you will have to tie that new relay into the high beams circuit too - basically you should not have the reduced DRL voltage and the full high-beam voltage applied to the lights at the same time, so the new relay will shut power off to the DRLs whenever the high beams come on. This is actually how I have my truck wired up, my DRLs are key-on powered and every time I turned the high beams on it resulted in light bulb overheat and explosion, so I just installed a SPDT relay right behind the regular SPST relay for the DRLs and now the SPST is still key-on triggered, but the SPDT one cuts the power off instantly when high beams come on... I realize this may sound entirely confusing, but it's real easy, and I can draw you a diagram if interested. By the way I am not an electrician by trade, and I absolutely hate wiring, so if I can do it then anyone can

 

Wow.

Thanks very much. I don't think I understand most of that but electrical is not a strength of mine. If you're willing, an diagram would be great.

What I'm really hoping is that I could isolate the circuit in the original harness that controls the drl and hook it back up. Unless someone has already told me that isn't possible and I'm just not getting it.

I'm going to look for my camera and try to post up a pic of the headlight harness set up.

 

I cant help but say that although M.L.C's idea is great...probably the way I would do it if I rewired my truck... it requires quite a bit of new wiring and several relays.

We know that the DRL module powers the hi beems at a lower voltage when the headlights are not on and when the truck is running. The LMC harness gets it's relay switching power from the old headlights. Thats why the high beem come on when the DRL's are on... the DRL's triger the new hi beam relay in the LMC harness.

Now if you get you relay trigger from another source that is not in the same circuit as the DRL's then you eliminate the DRL's trigering the relay.

If you can locate the headlight hi and low circuits coming out of the dimmer switch or also known as the hi/low headlight switch (the switch on the collum on your truck) then you have the relay trigger wires you need to trigger the new LMC relays. cut those wires and run them to the trigger side of the new relays (make sure too cut the old ones) and your headlights will work and the DRL cant trigger them to come on when the DRL is active... although at this point your DRL's wont work either... but two more connections and they'll be running too

take the wires (high and low) that go to the headlights from the new relays and connect/splice them to the wires you removed from the relays, the old trigger wires or the old high and low headlight circuit... by doing this you allow the DRL module to power the hi beams (at the lower voltage) and give the DRL the signal that the headlights are on and to turn it's self off.

After allot of though into this mod and looking at the headlight and day time running light wiring diagram this should work... but I'm no expert and there is no info on how exactly the DRL module works so I've made some assumptions on how the module operates in regards to its turning off when the headlights are turned on. But looking at the diagrams it's clear that the DRL module is spliced into the high and low curcuit of the headlights so it must get something from those splices other than the ability to power the high beams.

Some good people here at FTE and where I live helped me figure all of this out and if anyone cares to comment on it PLEASE do!!! this is what I think is the easiest solution... two new wires from the high/low switch and a splice to the old headlights.

 

Well, the situation just got more bizarre. This morning my kids came inside to tell me that my headlights were on. I hadn't driven the truck since yesterday afternoon. I went outside and the switch was off and the ignition was off but the lights were on. I had to turn the truck on and off a couple of times and turn the lights on and off a couple of times before they would turn off. 10 minutes later my kids were back in to tell me that the lights were on again. I ended up unplugging the LMC harness and reconnecting the factory harness to get the lights to stay off.

What is going on here? Its been raining cats and dogs here for a week. Could water in the LMC relay cause the lights to go on when the switch and the truck aren't?