How to install a switch to cancel the Automatic Headlight (AHL) feature on some 1999-2002 fullsize GMTs that GM decided didn't need to ever be able to turn off their headlights.
Note: Your DRLs will still come on while in gear.
Parts:
1x Switch
1x 1.5 kohm resistor
Difficulty:
Easy
Time:
Less than a day
Credit to someone else on some other forum for the idea, I just decided to do it and type it out.
Note: Your DRLs will still come on while in gear.
Parts:
1x Switch
1x 1.5 kohm resistor
Difficulty:
Easy
Time:
Less than a day
Credit to someone else on some other forum for the idea, I just decided to do it and type it out.
- Disconnect the battery
- Remove the knee bolster panel to access the BCM
- Locate connector C3 (rightmost purple connector)
- Identify the white wire and the gray wire 2 positions to the right of the white wire (NOT the one next to the white wire)
- Shave enough insulation off the wires to make a good solder connection (or use t-taps)
- Connect your switch and resistor inline between the white and gray wires (see drawing below).
- Done. You can now finally turn off the headlights whenever you want (on a ~15 second delay since this just tricks the BCM into thinking it's daytime).
- Switch ON / Circuit CLOSED - AHL are CANCELLED, you may use the headlight switch manually if you wish
- Switch OFF / Circuit OPEN - AHL operate normally, the headlight switch is worthless
