Ht54039

About a month ago my bas ast light illuminated after restarting my car it cleared since then it's came on a few more times. Ive heard it's probably the brake lamp switch. Is there a process I can do to test to see if the switch is bad like hold my foot on the pedal and release or something? Also sometimes my brakes are weak in reverse but the light has never been on when that happened. I just want a way to see if the switch is bad without a tester to ease my fears because I'm out of town and won't be able to tale it in for a week.

joeljp

Folks on here tend to just change it and that generally fixes this very issue. It's pretty cheap and simple to replace. There are several posts on this.

thtguy

ours was caused by the steering angle sensor and the Yaw Rate sensor... believe me they are not cheap $$$$!

if you are ever driving down the road and the car jerks hard and the light starts going nuts then one or both of those are your issue.

hope that is not the case.

E-Klasse

According to the BAS brake assist literature from Mercedes, the system measure and learns how fast the driver presses the brake pedal in normal stops and then if the driver pushes it faster than normal, the system applies full braking because it assumes that this was a panic stop. There must be a sensor used for pedal speed that could be faulty as well.

ohlord

brake switch.
Under 20 bucks
diy similar to the w210 and that diy is on www.benzworld.org w210 diy section at the top of the forum.
autohausaz.com caarries the oem switch

cla12

after replacing the brake vacum servo, i have started to get the bas asr light illuminated,i have replaced the brake switch 2 times now with the same result,and i have observed that when having the brake pedal depressed the light stays off until the next time use the brakes ,the light then comes on when i release the pedal, can anyone give any advice?

Merc Tech Knysn

What was the diag code u got.