This is actually a pretty simple mod to do, if you know what you're doing. There's a lack of information on the net concerning our trucks in this area, so it took a LOT of digging to find out the information I needed in order to wire this up. I hope it helps out anyone interested in doing this mod.

**DISCLAIMER**
I am not an electrician, car technician, or professional installer. Tampering with your vehicle electronics could void your warranty, and possibly cause serious side effects to your vehicle. Please do this AT YOUR OWN RISK!


Things you need:
-DEI 545t Nite Lite Unit - This is what makes this mod possible I picked up one on eBay for $30 shipped

-Wire (Different Colors Makes it easier)
-Wire Connectors
-Shrink Wrap
-Electrical Tape
-Solder and Soldering Iron
-Cable Ties

First things first, disconnect the negative side of your vehicle's battery. You are working with the electronics of your truck and in close vicinity of the driver's airbag. DO NOT skip this 2 minute step, it could save your life!!!

Now what are we trying to accomplish here? We want the DEI unit to trigger our headlights when it becomes dark. The DEI unit comes with 2 relays, however we only need one. Our headlights are triggered when a resistance of 660 Ohms is put onto the headlight circuit. Trust me, it's easier than it sounds.

Prep work. Although DEI supplies us with 2 relays, we really only need one. The relays are prewired, however we need to add a wire to the harness the DEI seemed to think we didn't need. Instead of talking colors, I will be talking about the relays poles by their corresponding numbers:



We need to add a wire to the 87a terminal of the left relay (or relay 1) of the DEI unit. Simply add a piece of wire to this terminal using a female quick disconnect connector:



Now simply push this up into the open 87a spot on the relay wire harness (it's the only open spot you have to work with). Now we can make our resistance wire. We need 660 Ohms of resistance, however my local radio shack did not have a 660 ohm resister, so I bought a pack of 470 ohm resisters and 100 Ohm resisters. I ended up having to daisy chain (1) 470 Ohm resister and (2) 100 Ohm resister for an approximate 670 Ohm resistance, which ended up working fine on my truck:





Make sure you solder these resisters together good, then solder each end to some wire, and then protect that with heat shrink:



Now you can connect 1 end of your resistance wire to the 87 terminal on relay 1 of the DEI pack.

Now your prep work is done, go ahead and dismantle your truck. You'll need to take out the driver's kick panel (it's just snapped into place, a good yank will pull it out) Now take out the plastic piece beneath the steering wheel, there's two screws on the bottom of it, then it's just snapped into place. After you've got that off there's a metal piece that you'll also need to remove, directly under the steering wheel. 4 screws and you can set it aside. Your hood release and computer connector is on this metal piece, I just put it to the side.



You'll have to remove the radio bezel also, open your drink holder and look up, there's 2 screws under there you'll have to take out, then the bezel is just snapped into place. I've found the best place to get grip is on the driver's side, but it is a little hard to pry it off, once you get it off, unhook your HVAC controls and cigarette liters, and set it aside. Now we can take off the plastic molding around the instrument cluster. There's several screws around it that have to be taken out, you have to put your truck in low gear, then just pull the plastic out and then up, make sure to unhook your light switch before you pull it all the way out. Take off the plastic access panel next to the headlight switch, on the outermost side of the dash. Stick a small flathead in it to pry it off. After it's all said and done you should be looking like this:



Once you're hear you have to decide where you want to put your DEI unit. I chose the area beneath the cupholders. There's just a void of unused space here:



Now we can begin hooking up our wires. Go to the headlight switch connector. There are 2 Green / White wires on here, we are using 1 of them. The one we want is on pin 1. Look at the back of your headlight switch for the pin numbers. Once you've determined which one is pin 1, cut this wire, leaving enough room on both sides to strip and work with:



No turning back now. Now attach a wire on each side of the wire you just cut, enough wire to reach your DEI unit, wherever you put it. I recommend using 2 different color wires otherwise it might get confusing. I also recommend soldering these connections for extra strength, shrink wrap, and electrical tape also:



As you can tell in the above picture, I used a RED wire on the TRUCK's side of the green/white wire, and a BLACK wire on the SWITCH's side of the green/white wire.

You need to attach the RED wire (Truck's Side) to terminal 30 of our relay we prepped earlier. You connect the BLACK wire (Switch Side) to terminal 87a (the wire we added to the relay). Now take the Resistance wire we made earlier that's on terminal 87, hook the other end of that wire up to a good ground. I used the factory ground location, underneath the steering wheel, you'll see a bunch of wires on a copper plate bolted to the dash frame. I unbolted this, connected an insulated ring connector on the end of my resistance wire, also made another ground wire while I was there to hook up to the DEI unit later, and bolted everything back up.

Now you have to decide where you want your photocell to go. I didn't want to be able to see mine, so I pryed up the back of the dash where the infinity speakers would have gone had I got that package. I put a small piece of metal over the speaker hole, and stuck the photocell to it, running the wire down the speaker hole to the DEI unit. I snapped the dash piece back together, and that plastic molding now holds the photocell securely in place.

Now we have to hook up the basic wires on the DEI unit:
Constant 12v (Red): I ran a wire directly from the battery. I had already made a hole through the firewall when I ran amp wiring, so I just used that.
Ground (Black): This is the ground wire I made when we hooked the resistance wire up
Ignition 12v (Yellow): I used the driver's side cigarette lighter for this. Just strip (DON'T CUT) the Red/Yellow wire back, solder another wire to this, tape it up, and then hook that up to the yellow wire:



The other wires on the DEI unit I did not use. You can hook it up to when you turn your wipers on the your headlights come on, or when you disarm a factory security system the headlights will come on. I didn't want that so I didn't hook them up. There's instructions with the DEI unit if you want these features also.

Now we have everything hooked up, it's time to test it. Put the plastic molding back on around the instrument cluster (The one with the headlight switch) hook the headlight switch back up. Connect the negative side of the battery you unhooked earlier (you had better done that) and then pull out of the garage into some sunlight. Turn your key to the ON position. If there is adequate sunlight your headlights should remain off, and the use of the headlight switch should be normal. Now place your hand over your photocell to simulate darkness. After 5-10 seconds you should here a relay click and your headlights will be on. Take your hand away from the photocell and check to make sure your headlights are on. You have about 30 seconds before the DEI will sense the sunlight and kick the headlights back off. Congratulations you now have automatic headlights.

Tape all your wires up and cable tie them out of the way:



Reassemble your truck in the reverse order you took it apart. Congrats, you're all done!! Now wasn't that easy.

Something to remember. With the Switched 12v source I used the lights will remain on with the Accessory delay until you open the door. Also, your headlights will be switched ON until after you turn your vehicle off, which activates the headlight delay feature on our trucks. If for some reason you want to cancel this, just turn your headlight switch on and off as you're getting out of the truck, and you'll shut the headlights off, otherwise they'll shut off in 60 seconds or so.

Any questions feel free to ask. I apologize for the lack of pictures as my digital camera's batteries were dead when I started this. The pics were taken from my phone, which also was suffering from a fading battery. Sorry.

 

Maybe a dumb question but how does this work with Daytime running lights?

 

Very nice write-up

 

I'm pretty sure this will work with DRL's, the only difference is it will just turn your instrument lights on, and nighttime tail lights...

 

Thats pretty sweet.

 

I do like this little gizmo. It turns the headlights on at about the same time I would. It also triggers the fog lights, if the fog lights were on the previous time the headlights were on. If not, simply turn your headlights on manually when it's not dark, trigger your fog lights, and then turn your headlights back off. The next time the DEI unit triggers your headlights for you, your fog lights will come on as well.

Like I said, this was the one feature I missed dearly from my old truck (and when you get used to this, it's hard having to switch the headlights manually lol) I can't tell you how many times I've pulled out on the road with no headlights on. Downtown area is lit up pretty well, so it's hard to notice you don't have your lights on. Problem solved!!!

 

Have you tested to see how it reacts to both the DEI unit and the headlight switch in the ON position at the same time? Since it would then see the combined resistance, it could produce weird results.

 

When the DEI energizes the relay, it cuts out anything coming from the headlights switch. The truck side (the side that goes to the computer) is hooked up to the common (30) terminal of the relay. When the relay is not energized the circuit is completed through the normally closed terminal (87a) or the switch side. However when the relay is energized it completes the circuit with the normally closed terminal (87) or our resistance wire.

So basically our headlight switch is cut out of the picture when the DEI unit energizes our relay. However, the cargo light, and dome fader still work perfectly... Also if you have the headlight switch ON, before it gets dark for whatever reason, and the DEI unit senses darkness and energizes, there's no flicker of the headlights. They remain on solidly.

 

FYI.... I picked up a pack of 330 Ohm 1/2 watt resistors at Radio Shack, used 2 of them in series for a total of 660 Ohms.

And a word about soldered connections on vehicles; ever notice how you never see many soldered connections on cars and trucks? When I was going through training to do electronic repairs on helicopters in the Army, I asked why we didn't repair wires and connections by soldering. The reason behind not doing it is that with extended vibration (which granted is much worse in a helicopter than a truck), solder joints can crack and give you a "cold solder" connection, a intermittent connection that is sometimes impossible to detect visually. Personally, I stick with crimp connectors most of the time, though I have been known to crimp and then solder a connector sometimes. I doubt that many people would ever have a problem with a solder connection, though; just passing on info.

Addendum: After doing a couple of searches about automotive connections, my thoughts above were confirmed.

"Soldering is a no-no. All manufacturers dropped soldering somewhere in the '60's... On wires and joints....unlike on a wave soldered circuit boards....there is no way to ensure that the solder connection is free of air pockets (voids)...which hold moisture and acid flux and start corroding from inside almost immediately.....are also structurally weak to vibration and prone to heat cycling and external humidity because line joints like this are almost impossible to varnish properly.....in an oxygen free environment like wave soldered circuit boards are. In short its a Short high resistance life.

The best way is butt connectors....but not those crappy red blue or yellow plastic covered ones like you find at a hardware store. Use non-insulated, non strain-reliefed ones....and don't use a pair of crappy $12 sheet metal wire crimpers from Radio shack. Use a REAL pair of factory style crimpers that produce crimps whose compression is exactly uniform in size and depth each time and for each wire gauge. The compression on a crimp made with this tool is measured in the TONS! You can get one from www.paladintools.com . Try the 1300 series with replaceable anvils and variable depth and pressure settings. Two sets of anvils/dies will crimp every connector your car will ever need (including fuel injection)....just like factory for around $100 for the whole thing.

Once you crimp the butt connectors...heat each one to about 200F with a heat gun, vanish is with circuit varnish and slip on a piece of heat shrink tubing. Then varnish the whole set of joints again. This will last longer than any solder joint, be mechanically stronger and be waterproof."

Personally, I keep a pair of Klein crimpers in my toolbox; very handy tool, top quality, you can get it for less than $25 at Lowes. http://www.lowes.com/lowes/lkn?actio...amp;lpage=none. Another thing in my toolbox; a butane mini-soldering iron from Radio Shack (http://www.radioshack.com/product/in...entPage=search). $20, no dragging cords outside, and it's got a torch tip you can use on your heat-shrink.

 

bwhite757 Said the following:

Maybe not, but you are obviously better than most "professionals" that may work on someones truck if they took it to a shop. Congratulations on a well written and documented article. I was in the electrical/electronics business for 40 years and you sure sound like someone that has more than a cursory knowledge of the field.


SmittyRN, kudos to you also for providing the excellent information on soldering vs crimping wiring connectors. After all the, shall I just say, less than helpful information I see posted on this forum by some people on various subjects, it is indeed refreshing to see information given by you two gentlemen that is both, factual and informative.