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Yet another brake lights on all the time post

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by Looops, Mar 4, 2016.

  1. Looops

    Looops Member

    Sep 11, 2011
    Hi all.

    Yet another brake lights on post but...

    About to throw this PITA W203 C 240 away. I will pass a MOT but has a problem with the brake lights stuck on even with the brake light switch removed. I had this question in the /brakes forum but thought I'd try my luck here.

    I've replaced the BAS/ABS module to sort out a BAS/ABS error which seems fine now. Now 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.

    I've replaced the rear SAM with two second hand units the sellers swore were good.
    I've swapped every bulb in both rear light clusters.
    I've substituted the BLSW with links to replicate the NO/NC and no change.

    What makes this really odd is that the old BLSW was faulty on my multimeter. Also a previous owner had forced two incorrect bulbs into the light clusters.
    My wife has a 2003 CLK so when she wasn't looking I swapped front BAS/ABS modules over and the brake lights stayed on.

    I have a good scanner - Foxconn NT644 - would a Merc STAR do better?

    Any suggestions before I park it in the sea?

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