1998 Blazer in great shape with a new problem. The driver side brake light does not come on when pressing the brake pedal. That filament works the rest of the time.

• Left turn signal works as it should
• Right turn signal works as it should
• Hazard lights all work as they should
• Passenger side brake light works as it should when you press the brake
• CHMSL LED works as it should when you press the brake
• Driver side brake light is NOT working when you press the brake

Here is where it gets weird. Press the brakes and hit the turn signal, and

• Passenger side brake light works as it should when you press the brake
• CHMSL LED works as it should when you press the brake
• Driver side brake light is NOT working when you press the brake - unless the right blinker is on. Left blinker and it does not work.

I already replaced the brake light switch since it was cheap and easy to do. There is another thread here where someone seems to have the same problem, but no follow up with the solution. Is the next step the multi-function switch?

 

Most of the time this points to a fault in the grounding or a short in the brake light assembly.

Can do funny things. My auto-electric guy normally can tell from the behaviour which ground is faulty.

I would take the lamp assembly apart. Up to now I have fixed over a dozen such problems and all came down to corrosion or a ground not being connected to the proper assembly. Out of nearly 20 cases only 2 were related to cabling issues.

With a multi-meter or even just a bulb and two leads, one with a clip to clip to a ground check the wiring of the plug. So you can narrow down the fault.

Maybe some of our electrical experts can even point you to the right place.

 

It's easy enough to pull the housing the clean and check everything. Do you know if the grounds are independent? Since both filaments light up other than when the brake pedal is pressed, I assumed the wiring at the rear and housing were all good. But it's free to clean them up.

 

The easiest is to take it apart and have a look.

I have seen a lot of things on rear and front lamp assemblies. Some were filled with water half way up. In some instances all the internal metal parts had rotten away. Have a look, I would guess at least a 50/50 chance to fix it at the lamp assembly.

 

I did replace the bulbs originally, but did not check the wiring or grounds. The housings are watertight, and remember that the bright filament does come on for the turn signals and emergency flashers, just not for the brake light - when the turn signal is to the opposite direction.

 

have you fixed this?