This 2004 Chevrolet Trailblazer came in with the complaint that the two lower stoplights did not work. The CHMSL (Center High Mounted Stop Light) does work. I installed my pedal pusher between the brake pedal and the front edge of the seat.
I went to the fuse box under the driver’s side, rear seat and checked the vehicle stoplight fuse.
Power on both sides of the fuse, so the problem is further back in the vehicle.
Yep, the CHMSL is working but nothing else.
I removed the two phillips headed screws that held each light assembly in place and pulled the light assembly away from the rear of the vehicle. After the light assembly was removed, I removed the three screws that held the socket board to the lens. Once the socket board was off, I pulled out the upper most bulb for the stop light and this is what I found.
On these vehicles, I prefer to use a high quality plastic based bulb rather than the glass based bulbs. These vehicles came with the plastic based bulbs originally. The plastic tends to insulate the socket from the bulb heat. The glass bulbs seem to transfer more heat into the socket and melt both parts. To help keep this problem away on any vehicle, place the shifter into park or neutral and take your foot off of the brake pedal, when stuck in a drive through lane or stopped traffic. Of course keep safety in mind as well.
I replaced the boards and installed three new bulbs in each board. Heat damage is like a disease, you have to get rid of it all or it will come back. Whenever I check one of these type bulbs, I look for even the slightest signs of heat. One trick is to rub my finger length ways, along the wire leads and feel for rough surfaces. If I feel any kind of roughness, a new bulb is installed and the socket is inspected, cleaned and or replaced, depending on what evidence is present.
The old board had not been properly screwed down and as a result the opening in the lens assembly was distorted.
After installing the board (I had to find one larger screw), I used silicone sealer to fill the gap between the orange gasket and the lens assembly. I did not want water to get into the assembly.
Now all three stoplights work.