brake light circuit

mt_goat · 10-13-2002, 12:17 PM

Hi guys, I usually hangout on a toyota 4X4 forum but my wife's 97 328I has been driving us crazy with a brake light circuit warning on the computer and dash. I did a search for this problem expecting to have a ton of hits and got zero! Am I the only one having this problem?

I have replaced every brake light bulb, all 9 of them (7 in the wing thingy), and still can't stop it. After many pumps of the brake pedal while sitting in the garage looking through the rear view mirror I have found that every now and then the brake lights don't light up when the pedal is pushed. When this happens none of the bulbs will light up. Then with the next pump of the pedal they all light up fine. Is there a common problem with the switch or wiring somewhere?

Thanks for any input,

SuperWheel · 10-13-2002, 11:28 PM

Okay, some more questions:

- Is the pedal pushed all the way down? If the switch is intermittant, then you may be having this problem.
- How's the brake fluid? The warning light often doubles for bulbs/ebrake/fluid. I can't remember on the late E36s if it does.
- I have also heard of newer low-resistance bulbs causing problems, but your car is too new for that
- Are all of the bulbs installed properly? If they are installed incorrectly (happened on my truck), they can create shorts, bad connections, and even an occassional meltdown/fire!

Hope this helps, do you have any more clues?

mt_goat · 10-14-2002, 02:56 PM

Yes, the brake pedel was pushed all the way down sometimes very hard and still no brake lights would come on. But then I would let it off and push again and every light would come on. The brake fluid is full, and every bulb socket was been checked 3 times for corrosion, dirt, looseness, etc. I've looked for damaged wiring but it all seems fine.

I found while doing a search on the unofficialbmw.com bulletin board that alot of people are having this problem and that replacing the brake light switch often will fix it. Some said they have had to replace this switch 3 or 4 times while they have had the car. So I will try that.

Thanks for your help,

Wayne 962 · Wayne 962's Garage

Ahh yes, the switch is the first thing that I would have looked at, but it is indeed a good idea to make sure that all other basic things are working first.

Is this switch located on the MC, or on the pedal cluster?

-Wayne

Bravo · Bravo's Garage

I am having the same problem. I replaced the switch and all was good but then yeaterday I got the same error! If you can figure this out I will be stoked
Dean
1994 325i

Wayne 962 · Wayne 962's Garage

Egads, I hate when that happens.

Again, check the other things. The brake light has many purposes. Unfortunately, the engine code reader doesn't read any codes for brake failures...

-Wayne

mt_goat · 10-15-2002, 07:05 AM

Well, I replaced the brake light switch and so far no problems! Only time will tell though because sometimes it would be ok for days without this problem rearing its ugly head.

The switch is located behind the brake pedal and you have to remove the lower part of the dash to get to it. It is lucky am into yoga because you have to stand on your head and twist into a small space with your cheek next to the brake pedal to get a look at it. I was able to remove the old one without breaking it but I hear that those with less yoga skills just break the old one with visegrips and rip it out (it is plastic). It is actually fairly easy to get out once you see one upclose and see how it locks into its little mounting hole. I had the help of a repair manual which had 2 good pics of the switch. For getting it out WITHOUT breaking it and for installing the new one you need to push the brake pedal down all the way down and at the sametime pull both the switch plunger and the plunger's sleeve as far out as they will go. In installing the new switch the manual said to slowly release the brake pedal after getting the switch into place and it will self-adjust the lenght of the plunger to the proper tolerence.

The switch was $36.00 plus tax at the stealership (ouch!) I did see one on the web for $26.00 plus tax and shipping. But I was in a rush to get this thing back on the road again. Mine was the 4 pin switch I guess some beamers take a 2 or 3 pin switch can't remember which, but they were cheaper. And yes you should stop driving your car untill you get this thing resolved because every so often the brake lights are not working!!!! And as fast as these BMWs will stop believe me you want the semi-truck behind you to get as much notice as possible. I will never ignore this warning again. This is a REAL safey issue and I am pissed that BMW has'nt recalled them for this obviously unreliable switch which put my wife and I in danger.

Bravo · Bravo's Garage

Good point, I plan to pick up another switch today and replace it again.

I read in a previous post that sometimes you have to replace it several times to fix it. so Either the connections are not good or the switches are not quality. Scarry!

Dean

mt_goat · 10-15-2002, 07:43 AM

How long has it been since you replaced it? Maybe it was defective or you did'nt get it to self-adjust to its proper tolorence. The manual I borrowed said if you release the brake pedal too fast after installing the new switch it won't self-adjust to the correct lenght. And that no other adjustment is possible.

Wayne 962 · Wayne 962's Garage

Interesting stuff here. I'll have to do a tech article on this replacement for the website...

-Wayne

mt_goat · 10-17-2002, 08:25 AM

Well, it has been a few days now and so far so good. That switch might have done the trick. I'll let you guys know if the problem returns.

Thanks for everyones input.

SuperWheel · 10-17-2002, 12:06 PM

I've been having problems like this on and off too - I should probably do the switch replacement as well.

mike944 · 10-17-2002, 01:59 PM

It's almost definetly the switch. I had this problem on and off for 9 months in my '94 325i I scratched my head for a long time before i finally found the solution on the internet: Brake light switch. it's pretty easy to change, but unless you enjoy working upside down in tight spaces, take out the old switch by cutting the plastic thing that locks it in place with a pair of wire cutters.

Never had a problem since (6 months)

Mike

P.S. there are 2 different switches used, call for the part first, and they should be able to tell you how to tell the diference. I think one has 4 wires, and the other has only 2, but i'm not sure.

M3Wizard · 10-21-2002, 07:58 PM

I'll second the request for a technical article!