Brake lights on all the time - switch changed and set properly

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Looops

Member
Joined
Sep 11, 2011
Messages
45
Car
CLK230
Evening all.

My PITA W203 C 240 has a problem with the brake lights stuck on even with fuse 62 taken out.

I've recently replaced the BAS/ABS module to sort out a BAS/ABS error which seems fine now. Doing that job I disconnected the battery and it's since then the brake lights are stuck on with ignition on. I also replaced the brake light switch at that time and remembered to pull out the plunger and fit it with the pedal down.

I have a good scanner and it says B1048 Stored/Current. Circuit 54 has Short circuit to positive.
It also shows the brake light switch toggling on/off.

After a bit of research I bought from eBay a used rear SAM module with the same part number (different HW number though) but the problem remains the same however the one from eBay has some corrosion around the fuel pump relay, so much so the relay supplied didn't work. I installed my relay and it's fine but still the brake lights are stuck on.

I'm sending the rear SAM back to the seller because he shouldn't be selling modules with corroded terminals because it's a clear sign there's been water over the unit so who know's what's going on inside.

So what do I do now?
Buy another used SAM and hope?
Would a STAR diagnoses get any closer than my pretty good Foxwell scanner?

Either the SAM has an input telling the SAM to put the lights on or the module itself has an internal short or trigger.

The splatter on the PCB on the SAM looks like thermal paste but why??

Any great wisdom from you Benz Wizards?
 

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