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When I turn the lights on the parking brake switch illumination (in the switch, not on the dash) flashes on and off a few times then goes off. This gets registered in my C4 as error 5700 in component S76/15 which is the switch. The parking brake itself works perfectly. Seems obvious and a simple fix, replace the switch. I didn't see the need to spend lots of cash on a new unit so I got a second-hand one. The same thing happens. OK so I was unlucky, got another one. Same thing again. Am I just really unlucky or could something else be faulty? If i'm really unlucky then maybe the lamp in this unit is rubbish and I'll splash the cash on a new one. The flashing is sort of odd but if the lamp is an LED I can understand it as the driver could have failed.
I think its supposed to flash - it tells you something, forget what.... I see mine do it at times (I don't and have never had a fault related to this flashing behaviour)
what's the handbook say? is it saying ready to self disengage as u drive off - LOTS of fun when ABS sensors die (which is a normal feature of the car)
Thanks for the reply. I've had a good look in the manual; it's silent. Just to be clear this is the switch illumination light not the dashboard lights; these are on or off depending on the state of the brake and could well flash. I rarely use the parking brake so I can't be sure about that. It's pretty unimportant as its a switch I never look at (i'm impressed that you do) but I'm still building up to having a go at updating the telemetrics so I was trying to clear all the error codes first (i'm still plagued by an error in a radar sensor, which propagates a whole raft of other messages, but that's a whole other story). I think what I'll do is take on of the switches apart to see what is inside. Maybe the LED driver is in the switch.
I think the flashing is saying I'm on - but you are in a driving mode / conditions that 's going to make me turn off (if you drive away) - illumination is nothing to do with flashing to says some condition is / isn't met
Hmmm. Maybe but the flashing happens with engine off (brake on or off) and when the lights are turned on. Pretty sure its a fault in the LED illumination and I'm just unlucky to get 2 duff switches. I think I'll try to persuade my local dealer to get a new unit on the understanding that I'll buy it if the illumination comes on and stays on.
Could someone please check? That might be the easiest way to figure out if this is a problem or not (if its not then there might be something wrong with the brake but it seems OK ). Does the switch illumination come on with the lights? Does it stay on when driving? Does it flash under certain circumstances? Thanks to anyone who takes the time to have a look for me!
Could someone please check? That might be the easiest way to figure out if this is a problem or not (if its not then there might be something wrong with the brake but it seems OK ). Does the switch illumination come on with the lights? Does it stay on when driving? Does it flash under certain circumstances? Thanks to anyone who takes the time to have a look for me!
Just checked for you and it comes on when the lights are turned on. It also stays on. Below is a pic...
Hi, great photo; thanks. I'm pretty sure now that I managed to get 2 duff replacements. In my searches I also found some posts (not w221) where Mercedes have omitted the LEDs on some light switches (to save money!) and people have soldered on the missing LEDs to get illumination at all switch positions. This tells me that Mercedes does use LEDs in these switches and that the circuitry is inside the switch. It can therefore fail. Looks like I'll have to buy a genuine new one as this lamp appears to have a limited life.
Hi, great photo; thanks. I'm pretty sure now that I managed to get 2 duff replacements. In my searches I also found some posts (not w221) where Mercedes have omitted the LEDs on some light switches (to save money!) and people have soldered on the missing LEDs to get illumination at all switch positions. This tells me that Mercedes does use LEDs in these switches and that the circuitry is inside the switch. It can therefore fail. Looks like I'll have to buy a genuine new one as this lamp appears to have a limited life.
I have an update. After trying 4 second hand switches I finally gave up and asked my Mercedes dealer to investigate. They wanted £40 for the work which I reluctantly agreed to. Of course they then ordered a brand new switch; same problem! In fairness to Mercedes they didn't charge me for the work for the switch but the illumination still doesn't work. Mercedes confirmed that there is voltage on the cable to the light and connected a regular bulb across the terminals; which worked! This is now completely baffling to me. Does anyone have any suggestions as to what could be wrong? Does anyone have a diagram of the pin layout for this switch? Has anyone taken one apart; I would like to have a look inside but I want to be sure that I can get it back together first? I know this is a really small thing but I hate mysteries.
- You can actuate the parking brake with your scanner to test it.
- It might also be a faulty wheel speed sensor which detects a moving vehicle while standing still.
Hi, thanks for your input but perhaps my post was not clear. My parking brake operates correctly. My problem (and I did say it was small) is that the illumination inside the switch has stopped working. That's all. As i've tried 4 second hand switches and Mercedes tried a brand new on and they tested the voltage on the cable I am baffled.
Hi, thank you for your input. All of my wheel sensors are original and the car doesn't have any other faults which rely on the wheel sensors e.g. ABS. I also don't see why a wheel sensor would affect the parking brake internal illumination (this is not the warning light on the dash). Like I mentioned this fault is trivial but the only one that still shows up on my STAR scanner.
the ABS sensors are used to trigger the auto park brake release - they inform the car when a driver (who has the park brake enabled) and has chosen not to manually release, is driving away... hence points in my first posts ages back
when the design to fail ABS sensors at the rear of the car give up, the park brake can go a bit mental
after my initial replies - I looked a few times for strange colours, flashing elements at various time or any illumination of mine and as I recollect nothing happens - as one can't see the switch when sat at the wheel (due to the incompetent design - out of ones eye-line) and it auto releases if one can't remember how to drive, whether it illuminates or not is a trivial matter
2007 S600, 2007 Chrysler 300 SRT8, 2000 C5 Corvette, and 2017 Mustang GT, and just got a 2023 300C
I suppose you will have to trust me. It is definitely a wheel speed sensor and probably a rear, but don't just replace one. BOTUS, who is one of the more knowledgeable and discerning members of this forum, has explained it to you. You just need to listen.
Martin.... Like a fussy mistress the car will always have something to ***** about when queried. Usually a dozen or more things to ***** about... none of which really effect how the car operates. Yours has one. Deep breaths.... Let it go. LOL.
03-07-2024, 10:21 AM
