All the brake lights went out on my SLK, similar to what Christopher described here https://www.slkworld.com/threads/slk32-2002-brake-light-issue.574648/ and David described there https://www.slkworld.com/threads/fa...m/threads/failed-brake-lights-all-three-is-there-a-relay-in-the-circuit.575364/.
As I have Eagle Eyes LED brake lights, I decided to check everything again.
I tested fuse #2 (good), the lights themselves (good), the brake switch (good), measured the voltage on fuse #2 while pressing the brake pedal - the voltage went from 12V to 0, confirming it was the light controller.
They're pretty cheap here in Germany (€50-100), but I wanted to get my car back on the road quickly, so I decided to see what was in the box.
Be very, very careful when removing the switch handle, it is held in place with two clips that are quite stiff but could easily break. You can then remove the cover by undoing the clips.
It turns out to be a very simple device, the actual commutation is completely mechanical, the circuit is only responsible for monitoring.
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The monitoring circuit is pretty much taken from the reference schematic of the U2481B/U2482B (Automotive Lamp Outage Monitor) and there is not much that can go wrong with it.
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The main PCB is made of flexible material (copper sheet?) and wrapped around the light switch. In my case, one of the fuse connectors was badly soldered, but it's actually soldered on the inside of the PCB, so I had to unsolder one side to get to it. Be very careful with the PCB, use a pre-heater and a solder sucker.
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I re-soldered all the fuse connectors just in case and reassembled the module, all works fine!
Hope this helps you diagnose similar problems.
As I have Eagle Eyes LED brake lights, I decided to check everything again.
I tested fuse #2 (good), the lights themselves (good), the brake switch (good), measured the voltage on fuse #2 while pressing the brake pedal - the voltage went from 12V to 0, confirming it was the light controller.
They're pretty cheap here in Germany (€50-100), but I wanted to get my car back on the road quickly, so I decided to see what was in the box.
Be very, very careful when removing the switch handle, it is held in place with two clips that are quite stiff but could easily break. You can then remove the cover by undoing the clips.
It turns out to be a very simple device, the actual commutation is completely mechanical, the circuit is only responsible for monitoring.
The monitoring circuit is pretty much taken from the reference schematic of the U2481B/U2482B (Automotive Lamp Outage Monitor) and there is not much that can go wrong with it.
The main PCB is made of flexible material (copper sheet?) and wrapped around the light switch. In my case, one of the fuse connectors was badly soldered, but it's actually soldered on the inside of the PCB, so I had to unsolder one side to get to it. Be very careful with the PCB, use a pre-heater and a solder sucker.
I re-soldered all the fuse connectors just in case and reassembled the module, all works fine!
Hope this helps you diagnose similar problems.
