I don't have a truck.
Jan 23, 2011
Argyle, TX
1. Gather up everything you will need

A 1K (1000) ohm resistor, 1/2 watt (available at radio shack for 99 cents a pack)
Wire strippers
Electrical Tape
Soldering Iron
Flathead screwdriver

2. Get your fingers up underneath the defroster output on the dash and start pulling. You may need to use your flathead screwdriver to convince the first clip to come loose.


3. Keep working your way all the way down until you have unclipped 6 or 7 clips that hold on this piece.



(If you really want more room to work, you can remove the side pillars and you will be able to flip this piece up for more working room, but its not necessary.)

4. Now we have access to the ambient solar sensor in the little bubble on the dash. As you can see there are 2 wires coming off of the solar sensor, a tan and a black/white. We want to trick the BCM into reading signals that it is daytime all the time, so we have complete control over our headlights. By installing this 1000 ohm resistor, we are lowering the voltage sent just enough to trick the BCM.

5. Peel back the tape that is already on there, allowing for 4 or 5 inches of wire to be shown.


6. Grab your wire strippers and expose about a 1/4" section on both wires. When you strip it, make sure you move the wire strippers toward the light sensor, otherwise you run the risk of pulling a wire out of the sensor, or pulling the sensor out of its bubble.


7. Grab your resistors and trim a little bit off both ends of it, because the connections are so close, we don't want or need all that extra length on the resistor



8. Grab the resistor and wrap the ends around both sections of the exposed wire, like this. I don't know if it matters, but I had the brown band facing the black/white wire. You may want to do the same. Then make sure you have a fairly solid connection BEFORE we solder.



9. If you want to use T-taps, scotch locks, or w/e, be my guest but soldering is the only way to guarantee a solid, reliable connection that lasts. :imo

Grab your soldering iron and let it heat up for a few minutes and carefully tin the tip.

Then, touch the tip to your first connection right where the resistor and wire meet. Let it sit a few seconds and apply solder directly to the connection. You should have a large bead that will insure a good connection. Do the same for the other side, and let it cool for about a minute.

10. Tape EVERYTHING up so you will not have any of the sections of exposed wire touching anything else, and tape the resistor from touching anything else behind the dash as well.


11. Test your lights by putting a shirt over the sensor, or just trying this at night. If auto headlights are disabled, then you have a good connection and are ready to just clip the dash pieces back together. If it does not work, you need to go back and check both connections.



Q: Why would I want to disable my auto headlights?
A: When running HID's, ballasts draw much, much more power than regular halogen bulbs when they first ignite. By disabling auto headlights, we let the truck start, then turn the headlights on, making it much safer on the ballasts as well as much easier on the electrical system. Also, when it is dark and you cycle the key from run to start, the lights flash. Theoretically, by doing this mod, your ballasts would only fire once instead of twice, doubling the life of them! :crazy:

Q: Does this mean I don't need a relay harness for my HID's?
A: Always run a fused relay harness.

Q: What else do I need to do?
A: On NNBS trucks, you should pull the DRL fuses, so the HID's dont come on during the daytime. Click here for write up on removing DRL fuses

Q: My lights came back on in the daytime, WTF dude?
A: Were your wipers on? The BCM automatically turns the headlights on when the wipers are on, nothing we can do about it.


Special thanks goes out to JB for sending me the write up for the 99-02 trucks :worship: which I used, and for the motivation to go ahead and try this.

Also, If you want to try and make these connections at the BCM you can try. I have a Viper 5701 alarm and remote start and my Audiovox XM tuner both right down there by the BCM, so I didn't want to go removing any of that. In my case it was easier to do it right at the sensor.

And LTZ guys, I dont know how to get at the sensor for that dash but someone figure it out and post some pics.

DISCLAIMER: Do not bitch about the shitty pics, I know they aren't the best.

UPDATE: 10/03/10

BARBER has done a write up for trucks with the auto HVAC controls, here is is. Good stuff.


How-To for any GMT900 vehicles with 4 wires leading to the ambient sensor.

After pulling up the plastic trim piece, I reached in underneath of it and was able to give the sensor a turn to release it from the plastic piece. Used a small flat blade screwdriver I unplugged the wire harness from the sensor. I used the same 1k Ohm resistor as above and trimmed and bent it like so:

Of the 4 wires on the harness, the resistor will be plugged into the Black/White wire and the white wire. Can't remember which wire was which, but should be able to do so like pictured. Take it and plug it into the plug in like so.

Note: You can bend and insert the resistor with the brown band like I did. Unsure if it will make a difference, but I'd recommend doing it like mine.


Lastly, I used electrical tape and taped up the plug, covering up the resistor as well. I also took a couple pieces and put over the female end on the sensor. The sensor got put back into the plastic trim piece and the wire harness was tucked away under the dash. Make sure to not get it stuck into the defroster vent. Test your lights and it should work. It worked for me.


New Member
May 16, 2011
Just so you know, don't worry about which way the resistor faces. They work fine either way.

Are HID's much better than the denali projector beams?

Thanks for the writeup!


If you unplug the sensor, it makes the vehicle think its night all the time. Using the resistor makes it think its day.

Good write up! Followed this in the Canadian Tire parking lot lol