How to test for a faulty BAS/ASR switch

[robs-mbz]

Having been helped out again by this A1 forum, (BAS/ASR warning) I thought I would add contribution. If you have a similair message displayed and want to prove that it is the brake switch that is faulty, try the following.

Gain access to the brake pedal by removing the trim panel below the dash.

Once you have found the brake switch you will notice that there are two plug connections, one smaller than the other. The larger of the two activates the brake lights, the other, small one is the connection to a normally closed contact for the BAS/ASR circuit.

Remove the smaller plug and short out the two pins in the head of the plug with a short length of wire, switch on the ignition, start the engine and hey presto, no more BAS/ASR warning!

To remove the switch, press in the small catch on the right hand side of the switch and rotate it one quarter turn clockwise, the switch then pulls out of its socket.

I took the trouble to dismantle the switch, the spring contact had broken, rendering it useless.

 

[jibcl500]

Glad you sorted it, wonderful thing the interwebby isnt it.

jib

 

[swiftymerc]

thanks for the info mine has just gone this weekend ?
anyone know what to expect to pay for one from a main dealer or can i get one from a non gen merc parts dealer?

 

[horgantrevor]

thx so much really thank you

 

[avanguard]

Having been helped out again by this A1 forum, (BAS/ASR warning) I thought I would add contribution. If you have a similair message displayed and want to prove that it is the brake switch that is faulty, try the following.

Gain access to the brake pedal by removing the trim panel below the dash.

Once you have found the brake switch you will notice that there are two plug connections, one smaller than the other. The larger of the two activates the brake lights, the other, small one is the connection to a normally closed contact for the BAS/ASR circuit.

Remove the smaller plug and short out the two pins in the head of the plug with a short length of wire, switch on the ignition, start the engine and hey presto, no more BAS/ASR warning!

To remove the switch, press in the small catch on the right hand side of the switch and rotate it one quarter turn clockwise, the switch then pulls out of its socket.

I took the trouble to dismantle the switch, the spring contact had broken, rendering it useless.

thanks for your advice , I just had the AA man checking mine , the footbrake releases but the light stays on , he could not find the switch behind the pedal ,any advice on where the switch is exactly located ?

he did take the cover off and tried lubricating the mechanism ,it works ok and the pedal comes back up but the light stays on ,when you push the pedal back up with your foot you can see the light go off but when you let go it comes back on again.

 

[charlie mc]

Hi guys. Got first M/B[220cdi V-reg] Fortnight ago,last week 'dash' showed bulb fault, was n/s brake bulb-changed it & thought was sorted as dash was ok again. But when put foot on brake BAS/ESP lit up...& NO brake lights!!So got new brake switch [ just fitted ] Followed robs-mbz tips to locate, remove, replace etc. [ otherwise I would'nt have had a clue about ] BUT Still no brake lights & BAS/ESP still light up as soon as put foot on brake-IF don't touch brake BAS/ESP does not light up. Any tips would be most welcome ...Thanks.

 

[tjamesbo]

TRy the brakelight fuse if no brakelights

 

[charlie mc]

TRy the brakelight fuse if no brakelights

Tried & tried again-No joy there..Thanks...

 

[garyfishball]

Thanks Rods, my CLK 320 1999, just had that problem, got a switch from ebay and fitted it in 5 mins, problem sorted.
It's a very good tips.

 

[RGM]

Going to try this. Mine lights up sporadically along with the ABS light. Though its not permanently on so was thinking brake sensor?

 

[television]

Once the brake lamp switch fails, the fault stays, many reasons for an ABS lamp to be on. if the warning is off while the car is not moving it normally shows that the sensors are OK, if it comes on as the car moves it shows that a sensor cannot read somewhere