About 3 1/2 months ago my 2003 Buick burnt out its drivers side daytime running light (which is also the turn signal/parking lamp).
Fast forward to this month. I've gone through 4 bulbs since the original burnt out. Thinking it was an electrical problem, I started by looking at the bulb socket and all of its connections. I back-probed the connections with the car running (DRLs on), with it off and parking lamps only, with the car running with headlamps on and with the turn signal on. I got readings all over the place.
There are 3 pins on the socket harness input and 4 contacts in the socket for the bulb (4157NAK). Depending on which "mode" the lights were in the center pin was sometimes acting as ground and sometimes as the positive (as verified by my multimeter). Voltage was also all over the place. From 12.8-13V and as high as 14.5-15.2V. With the DRLs which only has one filament lit, I was getting a 14+V reading from two of the pins to the ground, so instead of just one circuit there were two operating at the same time. When the turn signal was turned on things got even stranger with both circuits "blinking" (peaks and drops in voltage).
In order to make the DRLs function, GM takes the output from the turn signals and light switch (park/low beams) and runs it to the Body Control Module. The BCM in turn passes these feeds along if you signal a turn or if you turn on the parking/driving lamps. If you're not signaling or don't have your headlights on the BCM passes a constant 14.5V or higher voltage to the turn filament to act as the DRLs.
The problem with this is the voltage is too high. The bulbs are rated to operate at ~13V, not 14.5 or higher. This causes the contacts on the "hot" terminal in the bulb socket to overheat. It also causes the lead wire on the bulb to overheat and melt the bulbs plastic base. The bulbs still operate fine so long as you make electrical contact after the "burnt" portion of the lead wire but are worthelss in the socket. Eventually the sockets will melt if the problem persists for too long.
The solution. Disable the DRLs but cutting the 4 wires in the BCM harness that control the left and right front turn signals. Cut the light blue and light blue/white stripe and splice together. Cut dark blue and dark blue/white stripe and splice together. Ta Da! The BCM is bypassed for turnsignal operations. No more DRLs and no more overheading bulb and socket.
If anyone else has this issue here's a link to the directions.
http://www.lightsout.org/disable.html
Fast forward to this month. I've gone through 4 bulbs since the original burnt out. Thinking it was an electrical problem, I started by looking at the bulb socket and all of its connections. I back-probed the connections with the car running (DRLs on), with it off and parking lamps only, with the car running with headlamps on and with the turn signal on. I got readings all over the place.
There are 3 pins on the socket harness input and 4 contacts in the socket for the bulb (4157NAK). Depending on which "mode" the lights were in the center pin was sometimes acting as ground and sometimes as the positive (as verified by my multimeter). Voltage was also all over the place. From 12.8-13V and as high as 14.5-15.2V. With the DRLs which only has one filament lit, I was getting a 14+V reading from two of the pins to the ground, so instead of just one circuit there were two operating at the same time. When the turn signal was turned on things got even stranger with both circuits "blinking" (peaks and drops in voltage).
In order to make the DRLs function, GM takes the output from the turn signals and light switch (park/low beams) and runs it to the Body Control Module. The BCM in turn passes these feeds along if you signal a turn or if you turn on the parking/driving lamps. If you're not signaling or don't have your headlights on the BCM passes a constant 14.5V or higher voltage to the turn filament to act as the DRLs.
The problem with this is the voltage is too high. The bulbs are rated to operate at ~13V, not 14.5 or higher. This causes the contacts on the "hot" terminal in the bulb socket to overheat. It also causes the lead wire on the bulb to overheat and melt the bulbs plastic base. The bulbs still operate fine so long as you make electrical contact after the "burnt" portion of the lead wire but are worthelss in the socket. Eventually the sockets will melt if the problem persists for too long.
The solution. Disable the DRLs but cutting the 4 wires in the BCM harness that control the left and right front turn signals. Cut the light blue and light blue/white stripe and splice together. Cut dark blue and dark blue/white stripe and splice together. Ta Da! The BCM is bypassed for turnsignal operations. No more DRLs and no more overheading bulb and socket.
If anyone else has this issue here's a link to the directions.
http://www.lightsout.org/disable.html
