While this is more of a modification than a repair, I decided to post it here. However, I did consider posing it in the "Pet Peeves" thread since it definitely qualifies.
Situation: Due to GM's misguided effort to save a buck or two, my new Chevrolet Bolt EUV has a totally stupid yet legal brake light system.
There are 7 red lens lights on the rear of the car:
- a small brake/turn signal light located low on each side, below the level of the lift gate.
- a large tail light (actually two lights, one on the lift gate and one on the car body) located on each side, at the mid point.
- a "third brake light", located above the rear window.
One would expect the two (actually four) prominent lights located at the mid-point would be the brake lights. That's what drivers would be watching if they were behind an EUV in stop and go traffic. But no, they aren't brake lights. They are running lights that illuminate only if the headlights or parking lights are on, they do not illuminate when the brakes are applied. The lower photo below shows the location of the rear lights and the three lights that illuminate when the brake pedal is pressed.
While this configuration does meet federal regulations it is clearly a poor design, one that will almost certainly lead to increased chances for rear end collisions. On an EUV owner's forum, many report being told by other drivers that their brake light weren't working. One reported being pulled over and issued a warning for inoperative brake lights.
Lots of discussion on the EUV forums about what to do about the situation beyond complaining to the NTSB. The location of the wiring to the existing brake lights makes it very difficult to tap into them to link them to the large mid-point lights. Some owners added a rapid flash device to the 3rd brake light, which is an improvement, but not a solution.
I don't want to bore you further by getting down into the weeds too far about the idiosyncrasies of how the lights are wired, and why that prevented the end result of the modification being ideal, so I'll just describe the modification.
Since no wiring diagram is available to the general public (at least none I could find), I held a probe and test session with a voltmeter and the wiring bundle leading from the car to the lift gate. I located the three wires powering the 3rd brake light and the left and right running lights. I tapped into the 3rd brake light wire and connected a diode, then to the diode I attached a wire to each of the running lights. Now when the third brake light illuminates, the left and right running lights also illuminate as shown in the top photo below.
The diode prevents the flow of current the opposite direction, so the third brake light does not come on when the headlights are on and the running lights illuminate. The downside of this mod is when the headlights are on the running lights are on, so the only lights illuminated when braking are the original three. The end result isn't ideal but I'm not concerned since we do very little driving at night so the headlights aren't used that often.
Really frustrating that I felt it necessary to do this on a new car because GM thought saving a few bucks was more important than reducing the chance of a rear end collision.
On a more positive note, everything else about the car has been great!