A few days ago I picked up a brake light (or stop lamp) switch from my MB dealer. It only took about 30 minutes to swap it out properly. My problem is not fixed. Here is what happens.

This only happens when it is about 45 degrees or below. Strange. It also only happens when the car is cold and driven for the first time. IE: Every morning when I go to work it does this.

When I drive the car to work, I generally drive it gently and zone out as I listen to talk radio. About 2 miles into the trip, at about the same engine temp every time.... the BAS/ASR light comes on. The readout just says "BAS" on the display. I reset the display by clicking the "R" button on the dash and I go on my merry way. If I turn the car off and then turn it back on, the light does not come back on. It only does this once, when the car is cold and when the temp is below 45 degrees.

I thought that replacing the switch would solve the issue, but it doesn't. The ratcheted plunger on the switch was measured exactly to the same length as the old ratcheted plunger. I'm still very frustrated and am wondering if I need to have the OBDII readings taken to see if anything will pop up.

If anyone can give me any input on this issue, it would be humbly appreciated. Thanks in advance.[8D]

 

Hi Scuddog.

Temperature often adversely impacts electronic component performance.
Trouble is, which component.
Too often people (including the dealers) just keep swapping out boxes till by chance they are successful.
At considerable cost to whoever is paying!!
For this reason modern systems are fitted with diagnostics.
Diagnostics aren't bullet proof but do give valuable data, even if the data is "No Codes" set.

ABS, ASR, BAS system bus cannot be accessed by an OBDII scanner. You need more specialist equipment + MB dealer or an independent with top end equipment.

Get the codes, or lack of them, read for the BAAS etc systems.
Ensure you get a hard copy report with all vehicle details etc VIN number included. This is chargeable but = about 15mins labour if that is all that is done. In the UK they charge about £25 if you can't persuade them to do it under "goodwill"

Appears that the issue is BAS rather than ASR if the message centre is only showing BAS.
Out of interest where did you read that the BAS light is designed to come on after a BAS stop.
Sort of makes sense BUT my SLK and S Class don't.

Stuart

 

Stuart, thanks for the info. I appreciate the candor and upfront analysis. I will take your words to heart. I will contact my indie mechanic and see if he has the tools to diagnose my issue as you stated. He works full time at the local MB dealer and works 2 evenings per week at the mostly Volvo and BMW shop that I go to. He only works on the Benzes and they schedule work around his schedule.

Anyway, I had the BAS light come on once. I was on a country road and an animal ran in front of me. I stood up on the brakes and was glad that I had my seatbelt on because the car stopped in mere seconds. I was amazed. It was a violent stop. The BAS/ASR light was on and the info display read BAS. I freaked out as I thought that I had caused $$$$$ damage somehow. I'll dig up the info tomorrow but I believe that I found out from my owner's manual that the BAS light will come on after a really hard stop to let the driver know that the system was engaged. I'll follow up soon on that.

If my indie mechanic can't do what you recommended, I'll contact the dealer and see how "receptive" they are to an enthusiast with a miled-up, 11 year old E320. Ha!

Thanks again and best of luck to you in the new year![8D]

 

I'll go and read my manual re BAS as well!
Maybe I have the opposite problem to you!! LOL
Stuart