The brake pedal has a switch, I believe the booster does as well, however the switch I have in now is a URO brand switch it works intermittently, the MB one I put in failed instantly and never once worked so that is why I think it's the switch. The brake booster also has a plunger but I've never read on here of it going bad.

Got the new Brake Light Switch in today, reset the plunger, depressed the brake installed switch, let it self adjust. Start the car tap the brakes and BAM.... BAS/ASR light comes on again. I'm very frustrated at this point cause it causes no cruise control. I have no voltage at FUSE #2, ever, brakes depressed or not. The brake light switch wires go to a wire bundle and towards the engine bay, so where do they go? The light just about always comes on now and I have no brake lights, with a 3000 mile road trip in 6 days......if anybody has any more ideas I would appreciate it. I'm located in Yuma, AZ and the nearest dealer is almost 3 hours in each direction so a scan is out of the question...

Update: Today I noticed if I turn on the parking lights, I have no issues and the brake lights work with no BAS/ASR light coming on. I have to turn on the parking lights PRIOR TO THE FIRST TIME I TAP THE BRAKES! After that I can turn of my lights and hit the brakes as much as I want have no issues. The parking lights on was the only way to get my brakes lights to work. If the BAS/ASR light asserts then I flip the parking lights on and then my brake lights work, but the Dash light stays on till I restart car

To get further help, you really need to post a wiring diagram of the brake light circuit for the car in question. Random guessing is going to get you nowhere. The path from battery to ground needs to be diagrammed to figure out where the fault is occurring, it clearly isn't the brake switch or the bulbs.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

I've seen a single filament bulb jammed into a dual filament socket cause all sorts of issues ( the old style bayonet type not the newer plug in. )

Are there aftermarket electronics in your car like a security system, hidden radar detector or fancy stereo system? Maybe LED retrofits to OE lighting?

Sixto
98 E320s sedan and wagon
02 C320 wagon

No fancy electronics in gadgets, just an aftermarket stereo that's been in since I bought the car. Did the voltage regulator today and the voltage is much more steady. The brushes on the old regulator were just about gone. And the brake lights still work fine IF I turn on the parking lights first

Maybe look at the bulb failure unit ? , power has to pass through it to bulb ?

The rear tail and brake lamps share the same bulb socket. I would suspect that the issue is with the rear light assembly, socket, or ground (could be either side). I had a 99 wagon that threw the defective lamp code intermittently and that was due to poor grounding of the assembly. I've also heard of others swapping the left and right sockets and it working. These are frustrating to troubleshoot but at least you have a work-around.

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07 E350 4Matic wagon, 06 S430 4Matic, 99 SLK 230
retired W210 (x3), W124, W126

The w210s are a lot more complex that our old diesels. The electical diagrams are on WIS, but they are hard to use because the system uses a num ber of modules and what happens inside those is not explained.

When I had the ABS/BAS/ASR error, it turned out to be the ABS pump motor. When the car is first started, the system runs the pump briefly to make sure it is working (it does some other checks too) . In my case, the motor brushes were worn and motor only ran intermittently.

By the way, my brake lights still worked. Problem back there, is usually with the lamp holders.

KyleMP - Have you checked the Benzworld W210 forum? There is a wealth of information there. To solve your problem, you may need to get the car scanned at a dealer or indy that has Star diagnostics. There are likely codes stored that can help with diagnosis.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Late to the party.

Had the Identical problem in the shop about 2 weeks ago.

Headlight switch. It's a module as well...and all that stuff passes through it.

Pricey bugger new but I know they're on eBay cheap. Just get one with a warranty JIC.


Jono

Sent from my SM-G960U using Tapatalk

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