The Dude said:
Can someone tell me which wire there would varry in voltage so that I can connect an aftermarket radio dimmer to it in order for it to dim also?
Note, this information is for a 2002 model Av only, it does not apply to later years. I don't have any information on later years, so I can't help anyone who has a newer truck. Also, I have not tested any of this information, so use it at your own risk. This is my best shot based on reading the service manual, but I cannot gaurantee that this information is correct. Be warned.
There is a small dark green wire coming out of the headlight switch, but I
do not recommend that you tap in here. From the headlight switch it goes through a fuse. I
strongly recommend that if you are going to tap into this circuit, that you do it
after this fuse. If you don't, and you overload the circuit, you could burn up the dimmer portion of the headlight switch.
Really. I'm serious.
The fuse is in the left instrument panel fuse block (cover on the end of the dashboard, only visible when the driver's door is open.) It is a 10 amp fuse labelled "ILLUM"
I see two easy ways to tap into this circuit: The simplest is to get one of the little brass fuse tap clips that you can find at the auto parts store. Pull the fuse, lay the tap next to the blade of the fuse, then push both the fuse and tap back in the fuse socket. Make sure you place the tap on the fused (output) side of the fuse, and not the input side. You can verify the input/output side of the fuse by pulling the fuse, turning on the light, and using a meter to see which side of the fuse socket has power. Put the fuse tap on the other side. Once the tap is in place, you can connect your new circuit to the tap.
The other easy place to tap into this circuit is at the Body Control Module (BCM.) Remove the kick panel immediately under the steering wheel. This is held on by several screes: some are visible at the bottom of the panel, the others are visible at the top of the panel once you take off the dash bezel. Look carefully, don't force it, and you should have no trouble finding the screws. Once this cover is off you will see the BCM which is a small metal box with a row of three connectors on it. The connector you want is the purple one, and you want position A5. The connector has two rows of wires. One of the rows of wires has the following sequence of colors:
- A1 - Dark Blue / White
A2 - Dark Blue / White
A3 - Brown
A4 - Grey
A5 - Grey
A6 - White
A7 - empty
A8 - empty
You want the grey wire at A5, but
make sure you get the right grey wire! You want the one that is next to the white wire, not the one next to the brown wire! Use a ScotchLock connector to tap into that wire.
Whatever method you choose to use, I strongly suggest that you use a volt meter and test the circuit to make sure you have the right one. It should not have any voltage with the lights off, and the voltage should vary when the lights are on and you adjust the dimmer control.
Remember, like I said before, I have not verified this data on my own truck. Please be careful.
-- SS