Brake light switch question

[dtharp113]

My brake lights power on when I start my car. When I manually push the button on the brake light switch, they go off. I'll do some further testing this evening by unplugging the switch and seeing what happens (if the lights stay on or go off -- if the switch is bad, the lights should go off when unplugged, correct?).

Question is - when adjusting the switch, am i adjusting the switch forward (towards the radiator) so that when the brake pedal is depressed, it pushs the button closed? I'm having trouble visualizing how the levers move.

I realize I have a 50/50 shot at getting it right, but with losing the daylight so much more quickly, I'd rather take the correct approach the first time.

Thanks,

Dennis

[FB73tii]

If you just unplug the brake light wires from the switch the brake lights should go out no matter what, as you have cut all power to them. So are they on all the time except for when you manually depress the switch button? Has it always been this way, or is it a new car for you, or did it just begin and no other changes made? Perhaps the switch is just sticky, some electrical cleaner might help it. Sorry, I don't recall which way to adjust the depth of the switch, I'm using pressure transducers to trigger my brake lights now.

Fred '73tii and '69 GT3

[M3M3]

you answered your own question. if you push the switch, they go off. so...adjust the switch so that it is "pushed" more....ez.

[Dave_PA]

check the switch that is on top of your brake booster. you might need a hand having someone else push while you look. I had this problem a few years ago. it's a super easy fix. short term, have someone stand on the brake while you clean off the end contact, on both ends. long term get a new switch.

hth,

Dave

[Mike Self]

Switch is either out of adjustment or sticking.

To adjust, loosen the lock nut and screw the switch in so that the button is depressed when the brake pedal is released.

If it's sticking, have someone step on the brake pedal, drizzle a little WD40 on the black button, then press it in and let it snap out a couple of times. That should free it up.

Warning: if you let the brake lights stay on for any length of time, the bulbs will melt their inner--and eventually the outer lenses. Then it's new lens time.

cheers

mike

[dtharp113]

you answered your own question. if you push the switch, they go off. so...adjust the switch so that it is "pushed" more....ez.

I guess.. what's throwing me is there's a flat spot on the arm/lever that travels up from the pedal box from the brake pedal where the brake switch button rests. as i was doing this last night (with a failing torch...) I couldn't see how the lever actually moved.

So the normal (no brake applied) position is for the switch button to be depressed; when the brakes are applied, the button is released?

Seems a bit opposite, but whatever works...

Thanks all.

[M3M3]

"So the normal (no brake applied) position is for the switch button to be depressed; when the brakes are applied, the button is released? "

yes.

[Dave_PA]

So the normal (no brake applied) position is for the switch button to be depressed; when the brakes are applied, the button is released?

Seems a bit opposite, but whatever works...

Thanks all.

that's exactly it. it seems a little wierd, but it works. It's the same on my Datsun Roadster, but is INSIDE the car on the brake lever not on the MC.

Dave

[Mike Self]

If the switch was depressed (vs released) for the brake lights to come on, then the pedal position would be critical--a little bit of wear--or misadjusting the linkage--would cause the pedal linkage to press so hard on the switch that it would break it (mechanical advantage).

Every mechanical brake light switch I've ever seen is a "normally on" switch, not "normally off"

cheers

mike

[wegweiser]

I had to replace one hours before a road trip to Canada a few months ago. Naturally no one in the area had a 1968-1983 BMW switch, so I bought a plastic mid 80s Chevy Camaro switch to get me through the week. (lord forgive me) Worked great...now the correct factory style BMW one is in.

hardest part is loosening and adjusting it with little room for wrenches. A bit of trial and error. having a mirror behind you or a partner helps in determining when they're on or off, while you actuate the pedal.

[dtharp113]

Success! 10 minutes under the hood and the lights are sorted!

Thanks all!

[TobyB]

It's the same on my Datsun Roadster,

ironically, the switch on the '68 roadster failed, and, finding the

Nissan one to be both expensive AND rather unimpressive,

I replaced it with the BMW switch.

Now I stock fewer spares.

heh

t

[Dave_PA]

Lol!!!! Toby that is good to know!! The roadster does need some good quality German technology.

Are you on the 311s board??

[phano]

My apologies for reviving this years old topic. My stop lights aren't coming on when I depress the brake pedal. I'm continuing to troubleshoot and want to be prepared to replace the brake light switch if needed. Where can I find this switch  in the vehicle? I recently purchased my 2002 and we are just getting to know each other. Thanks in advance.

[John_in_VA]

It's the switch under to hood by the brake booster/master cylinder.  You'll see a pair of wires attached to it.

 

 

 

Edited December 11, 2015 by John_in_VA