Stopped for no brake lights !!

[Trueoo7]

Was out with my BDR driving today and was pulled over for no brake lights initially. He asked me to apply my brakes and nothing came on until I really applied pressure to them, similar to panic braking. Pedal traveled about 2" before lights came on. He let me off with a warning to get it adjusted, thankfully !! Unfortunately there is no adjustment on these BMW power brakes. I'm guessing its some type of pressure sending switch that controls the lights. Fluid is up to the top and brakes are hard and firm. I don't believe bleeding them is going to help. Has anyone else had this problem or can you let me know how much travel you have in your pedal before lights come on.

Hey Boudy, are you out there ?

Thanks
Trueoo7

[Red Era]

I had the same problem on my ERA. It has a switch that works off of the brake fluid pressure ( located on the master cylinders). Replaced the switch and everything was fine.

Good luck

[clayfoushee]

Those switches fail frequently, and likely to be your problem.

[Junket]

I had the same problem the pressure was on the master cylinder the gets the less pressure on the bias I installed a old style chev brake switch that goes on the brake peddle.
Ken

[Double Venom]

If it's a normal type pressure switch, follow your brake lines. It should be relatively close to the MC, but not necessarily. It will normally be installed in the line with a "T" fitting. It will look like a oil pressure sending switch but with two posts for your wiring vs. just one.

Out of the hundreds we have installed, I would say that 15% are bad or fail within months of installation.

For what ever reason (we're thinking an air pocket inside the switch forms) we have much better success with these switches if we place the connecting pins straight down.

DV... just another, "for what it's worth" post! Did I tell you BDR is coming to Da' Fling in force?

[BMK]

DV

That 'Fling' is just getting better and better.



Hope that the 'weendoggy' has that video up and running.




Cheers

[Rogers]

I was at a cruise-in....we left about 7pm to drive around the town before heading home. My wife was behind me....when we stopped she yelled...no brake lights! My Backdraft has just 500 miles...it now looks like another problem has been added to the extensive fault list.

[kountzecobra]

Best thing you can do is to install a mechanical switch on the pedal and forget about the Hyd. switch. They have always been a PITA. Some work forever, others work a very short while and are not reliable.

[jpfletch1]

After reading your post I went out to the garage to checkmine. NO brake lights. BDR #86

[clayfoushee]

Does the BDR have a manual brake bias adjustment on the pedal? If so, you might try putting more pressure on the front brakes before you replace that switch.

DV told you exactly how to find it, above.

[Trueoo7]

I think I found the switch, it is at the end of the master cylinder, inserted upside down in the unit, two wires are attached. Is this a generic sending unit available at an auto parts store or do I have to go to BMW to get a match? This ought to be fun replacing without getting fluid all over everything. If I try to convert over to the mechanical switch can I use these two wires coming off the sending unit now?

Thanks
Trueoo7

[petek]

Best of luck replacing the switch without fluid running all over everything! Been there, done that, bled the brakes afterward!

If your pressure switch is like the one I have, it makes contact when the system is pressurized. Converting to a mechanical switch that makes contact with the pedal depressed should be no problem at all; just use the same wires.

[Trueoo7]

Petek
Did replacing the switch solve your problem? Trying to weigh the difference between installing a new setup or trying to work with the existing one.

Thanks
Trueoo7

[Double Venom]

True,
If you have the ability, change the switch to mechanical! If you want to keep it as is, you can find it at NAPA. If it actually screws into the Master Cylinder then it may in fact be a BMW part.

May I suggest before you do either have someone press on the brake pedal...just once and hold. Run a continuity test across the pins, got tone? Not the switch. No tone, have your helper pump the breaks and test for continuity at the same time. Got tone now? Bleed the brakes. No tone...replace the switch.

DV...It's nice to run into a simple problem once in awhile.

[petek]

True,

I've got a pressure switch on one car (with no problem) and a mechanical switch on another car (with no problem). My preference is for the mechanical switch simply because it's a simpler switch and doesn't connect to the fluid system.

Do what DV suggests and check the continuity of the switch using a DVM or continuity buzzer; you'll quickly learn if it's the switch or something else.

[trularin]

Pegasus racing has those switches. Sorry, I do not have a number for them.

[tfarhood]

Same problem this past weekend. Had some friends following me, and they informed me that there are no brake lights. After checking fuses, etc., I found out it is indeed the switch. Easy test: Disconnect the two wires from the switch on the end of the MC. Place a jumper wire into them and turn on the ignition. Presto, brake lights work, switch doesn't. I rigged a temporary mechanical switch by running the wires to the pedal, and a piece of spring steel that work perfectly for the moment. I will probably change to a mechanical switch just to avoid messing with the brake fluid. I forgot to call Regg about it today to find out if it is a BMW part for the hydrolic switch or not. I'll let you know what I find out.

[CSCHWER]

I've noticed the same thing with my BDR. It's a combo of the light weight and manual transmisson that delays the light. I will probably install a manual switch on the pedal and just leave the hydralic switch in line also.

Chet

[Trueoo7]

Mine work, just not soon enough, I'm practically stopped by the time they come on. If you find a mechanical switch that works, please post it with part numbers if possible. I noticed that on my gas pedal frame there is a square plate with a hole in it off to the side of the pedal. Might be a place to mount an offset switch which extends over to the brake pedal if I can find the right switch. If I find something first I'll post it. If anyone talks to Regg about this, I'd like to hear if he has a fix as well.

Thanks
Trueoo7

[clayfoushee]

Jim Harding, one of our CACC members, installed a refrigerator "light off" switch on his brake pedal to avoid the problems of the fluid pressure switch. Was a very cheap and ingenious solution.

Perhaps you could do the same with those spare mounting holes.