The Good:
You can bypass the BCM controlled high beam/fog disable circuit in five minutes, for less than a buck.
The Bad:
You lose your high beam indicator lamp.
The Ugly:
You have to cut some circuit traces on the instrument cluster's circuit board and do some micro-soldering to get the high beam indicator lamp working again.
--
First the good:
Get yourself a 3M Scotchlok type 558 IDC (insulation displacement connector). ?The 558 has one pass thru port and one butt type port. ?It allows you to splice a stub of wire onto an existing line.
If you can't find one locally, I'll send you one for every one dollar you donate to the Chevy Avalanche Fan Club. ?Hurry, supplies are limited. ?
Next, pull off the knee bolster panel beneath the steering wheel. ?It is held in place with two screws on the bottom. ?Use a 7mm socket to remove them. ?Once the screws are removed, carefully pop out the top edge and set the panel aside.
Below the steering wheel, you'll see the three Body Control Module (BCM) connectors. ?Conn. 1 is brown, Conn. 2 is light-blue and Conn. 3 is purple.
On Connector 2 (light-blue) look for the purple wire along the top row, fifth from the right (position C2-B5). ?This is the "Headlamp Dimmer Switch High Beam Signal" input to the BCM. ?When this signal is at +12VDC, the BCM knows your low beams are on. ?When it is grounded, it knows your high beams are on (and turns off the fogs). ?Now here's the scary part... CUT IT. ?Make the cut two inches away from the connector.
Now look for the white wire (careful, there are two on this connector) that is on the bottom row, second from the end (position C2-A11). ?This is the "Headlamp Relay Coil Supply Voltage". ?Slide the Scotchlok over this wire, then insert the purple wire from conn. 2, pin B5 into the hole in the connector and push until it butts up against the end. ?Verify wire positions within the Scotchlok and crimp. To resolve the BAD and UGLY outlined at the end of this docement, stick the anode (non-striped side) of a small diode into the Scotchlok before you clamp it. Too verify a good connection, you might want to solder the diode lead to the purple wire.
What you end up with is something that looks like this (note the other half of the purple wire floating in the left of the pic):
What the mod does is allow you to go from this (fogs with low beams):
To this (fogs with high beams):
Now, in order to rectify the BAD and UGLY, you need to remove the instrument cluster. ?If you're still with me this far, my guess is that you already know how to do this.
Once you get the cluster broke apart... ahem, "disassembled", you end up with this (you don't need to take it apart this far, I was curious as how to hook up a tranny temp gauge):
What you need to do next is flip the circuit board over and cut the two circuit traces leading to and from the high beam indicator lamp. ?You can just make them out in the picture below. ?Next, I soldered some 3 ft. lengths of 30 ga. (not sure, but this stuff is small) to each solder trace where the lamp plugs in. ?I advise that when you plug the lamp back in, ohm from wire end to wire end to verify continuity through the bulb. ?Here's the only picture I have of this:
Next, take one wire from the high beam indicator lamp you added in the instrument cluster and solder it to the the diode connected to the Scotchlok connected to the white wire at C2-A11. I suggest using some shrink tubing to cover the entire connection.
Finally, tie the second wire from the high beam indicator lamp to the purple wire. I soldered the connection and covered with heat shrink, but a butt-splice crimpon will work too. ?
Also, it probably wouldn't hurt to use a length of heat shrink to act as a wire loom to protect the two wires along their route from the instrument cluster, down to the BCM (I used teflon coated wire). ?Here's a picture of what I ended up with:
As always, comments and criticisms are welcome and of course, you do this at your own risk.
You can bypass the BCM controlled high beam/fog disable circuit in five minutes, for less than a buck.
The Bad:
You lose your high beam indicator lamp.
The Ugly:
You have to cut some circuit traces on the instrument cluster's circuit board and do some micro-soldering to get the high beam indicator lamp working again.
--
First the good:
Get yourself a 3M Scotchlok type 558 IDC (insulation displacement connector). ?The 558 has one pass thru port and one butt type port. ?It allows you to splice a stub of wire onto an existing line.
If you can't find one locally, I'll send you one for every one dollar you donate to the Chevy Avalanche Fan Club. ?Hurry, supplies are limited. ?
Next, pull off the knee bolster panel beneath the steering wheel. ?It is held in place with two screws on the bottom. ?Use a 7mm socket to remove them. ?Once the screws are removed, carefully pop out the top edge and set the panel aside.
Below the steering wheel, you'll see the three Body Control Module (BCM) connectors. ?Conn. 1 is brown, Conn. 2 is light-blue and Conn. 3 is purple.
On Connector 2 (light-blue) look for the purple wire along the top row, fifth from the right (position C2-B5). ?This is the "Headlamp Dimmer Switch High Beam Signal" input to the BCM. ?When this signal is at +12VDC, the BCM knows your low beams are on. ?When it is grounded, it knows your high beams are on (and turns off the fogs). ?Now here's the scary part... CUT IT. ?Make the cut two inches away from the connector.
Now look for the white wire (careful, there are two on this connector) that is on the bottom row, second from the end (position C2-A11). ?This is the "Headlamp Relay Coil Supply Voltage". ?Slide the Scotchlok over this wire, then insert the purple wire from conn. 2, pin B5 into the hole in the connector and push until it butts up against the end. ?Verify wire positions within the Scotchlok and crimp. To resolve the BAD and UGLY outlined at the end of this docement, stick the anode (non-striped side) of a small diode into the Scotchlok before you clamp it. Too verify a good connection, you might want to solder the diode lead to the purple wire.
What you end up with is something that looks like this (note the other half of the purple wire floating in the left of the pic):
What the mod does is allow you to go from this (fogs with low beams):
To this (fogs with high beams):
Now, in order to rectify the BAD and UGLY, you need to remove the instrument cluster. ?If you're still with me this far, my guess is that you already know how to do this.
Once you get the cluster broke apart... ahem, "disassembled", you end up with this (you don't need to take it apart this far, I was curious as how to hook up a tranny temp gauge):
What you need to do next is flip the circuit board over and cut the two circuit traces leading to and from the high beam indicator lamp. ?You can just make them out in the picture below. ?Next, I soldered some 3 ft. lengths of 30 ga. (not sure, but this stuff is small) to each solder trace where the lamp plugs in. ?I advise that when you plug the lamp back in, ohm from wire end to wire end to verify continuity through the bulb. ?Here's the only picture I have of this:
Next, take one wire from the high beam indicator lamp you added in the instrument cluster and solder it to the the diode connected to the Scotchlok connected to the white wire at C2-A11. I suggest using some shrink tubing to cover the entire connection.
Finally, tie the second wire from the high beam indicator lamp to the purple wire. I soldered the connection and covered with heat shrink, but a butt-splice crimpon will work too. ?
Also, it probably wouldn't hurt to use a length of heat shrink to act as a wire loom to protect the two wires along their route from the instrument cluster, down to the BCM (I used teflon coated wire). ?Here's a picture of what I ended up with:
As always, comments and criticisms are welcome and of course, you do this at your own risk.
...
I mean how often to you really need your:
