On cold days(temp under 0 Celcius)the ASR malfunctions. Sometimes you can shut the car off and restrart it and it works fine for the rest of the day, other times it will come on three or four times, worse the colder the weather. Replaced brake light switch and cleaned all ground connections. Has anybody found any connection between ASR problems and the TPS(throttle postion sensor) as sometimes the ASR will malfunction without touching the brake, just by letting off the throttle or after hard acceleration on the highway the ASR will come on. Love this car but driving me to drink(more)
The Fireman

The usual - check the fault codes, do a search.

keeps indicating tail/brake light switch

I don't think there is a code for tail/brake light switch. There's one for stop lamp switch, code 5 on pin 7. If that's the code you're getting, and only code you're getting, and you're erasing it and it keeps coming back, that's where I'd focus.

Brake Sw. and Stop Sw. are the same S9/1 Switch.

On ASR chassis , the switch is a double circuit switch , one for brake lamps and one for ASR...however, the ASR is a Normal ON sw and the Brake is a Normal OFF, So , b/c you get an ASR code without pressing the brake means nothing. You could have a bad contact in S9/1- ASR section and that is why you can get a S9/1 code regardless of brake application.. There are two likely possibles ..one is the new sw you got was not from Benz..this is a common problem with after-market ASR switches. The second possible is b/c of the fact that the ASR is ON when pedal is UP, you have to make sure the sw adjustment is correct or the sw can be open due to improper adjustment.

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A Dalton