Brake light is permanently on!

[dj_efk]

Hi all,

My brake light is now permanently on after a complete system overhaul. I've looked at the switch in the resevoir and although there's space for two terminals it only has one (green) wire running to it - Should there be another wire running to it? I've attached a picture so you can see what I mean.

The car is an extremely early import to the UK from Germany that was imported by BMW as a LHD car then converted. Therefore it has a somewhat strange setup for the brakes involving two master cylinders.....

Thanks!

 

[61porsche]

Two wires. The other is a ground; preferably brown.

 

[dj_efk]

Hi 61, thanks for this, however I've checked and I cannot see another wire hanging loose anywhere looking for a home, especially where the green one pictured comes through the bulkhead?

 

[Stevehose]

Since the reservoir is plastic and not grounded, there should be a second wire for it to work. Strange.

Hi 61, thanks for this, however I've checked and I cannot see another wire hanging loose anywhere looking for a home, especially where the green one pictured comes through the bulkhead?

 

[61porsche]

Single wire to the screw next to the resevoir shown in your picture.

You need to add it.

 

[fredp]

I believe the red wire has lost the spade connector that plugs into the reservoir lid to the right of the wire already attached.

 

[Stevehose]

Here's a pic of mine, one brown and blue(?) wire and 2 browns into the other side. Then they get wrapped in tape and join the harness below the reservoir.

I believe the red wire has lost the spade connector that plugs into the reservoir lid to the right of the wire already attached.

 

[dj_efk]

Hi both,

Fred, the red wire is the ign live for the Lumenition Optronic setup I'm running that is mounted in front of the fluid reservoir out of sight in the pic.

Steve, thanks for taking time out of your day to take that pic, any idea why you might have two wires coming off the one terminal? I was thinking it could be due to you running a dual circuit setup but surely if the fluid level is low then that doesn't need two separate sensors anyway?

Next step I think is to add a temporary earth as 61Porsche suggests. I'll report back!

 

[Stevehose]

According to the wiring diagram the blue/brown goes to the parking brake switch and the dash light and the brown goes to test point 3. You may want to investigate the parking brake switch to see if it is working or not, this may be tripping the light on and not the reservoir. It doesn't make sense to me how a switch with one wire could cause your light to go on so it must be that your gauge light is being tripped by the handbrake and that you are not hooked up to the reservoir warning switch at all.

Why I have 2 wires I have no idea, unless it is wired in series with another device or something to do with the test point and ground but it doesn't show on the diagram.

Steve, thanks for taking time out of your day to take that pic, any idea why you might have two wires coming off the one terminal? I was thinking it could be due to you running a dual circuit setup but surely if the fluid level is low then that doesn't need two separate sensors anyway?

Next step I think is to add a temporary earth as 61Porsche suggests. I'll report back!

 

[dj_efk]

Thanks for that, are you able to post a copy of the wiring diagram online at all? It'd be great to restore functionality of the low fluid warning once I've sorted the handbrake switch.

On that note, where is the switch and how do I access it?

 

[Stevehose]

Here is a 72 wiring diagram, it may or not exactly apply to your car:

https://docs.google.com/viewer?a=v&...mMtNzlmYTIwZWFhN2Uz&hl=en_US&authkey=CNXcpd0E

I've never worked on the handbrake lever, but if you pull up the rubber boot around it the switch is probably under there, check for it shorting or other failure.

Thanks for that, are you able to post a copy of the wiring diagram online at all? It'd be great to restore functionality of the low fluid warning once I've sorted the handbrake switch.

On that note, where is the switch and how do I access it?

 

[deQuincey]

i had the same problem some time ago

hi, no, my wiring was ok, but let me explain the best that i can what happened to me

the same day i bought the car i noticed the red loght in the dash, and as i was a newcomer to the model i can not tell where this wascoming

it took a while until i realised that the parking brakewas the cause, but i relized that probably the cause was that the parking brake switch was quite in a wrong position and that wasdoing the malfunction, so i fixed it, and, alas, problem solved !

some days later after filling the fluids and changing spark plugs, and so on, (incidentaly, why don't we remember doing the changes one at a time:cry, i started the car and saw the dammned red light again, wow !, and what is happening now ?

i checked the parking brake, nothing !
i rechecked the brake fluid reservoir just refilled, and of course was ok
the i removed the cap, and checked the metal pin switch, and that worked well also,

then it came the question, i saw that if i reinstall the cap without paying attention to the way the metal pin switch of the cap, is contacting the floater rod, it has enough play to fall out of its centre, so the situation was leading to a wrong measure, exactly the same as if the reservoir was empty

please check this it might help you !!!!

pleaseif something is unclear just tell me

regards

regards

 

[boonies]

resurrecting a very old thread to add a solution:

I replaced the brake light switch about a year ago as I was working on my interior project. I found this week as I was getting the old girl warmed up that the brake lights were on continuously with the key switched on. After checking the items above I disconnected the brakelight switch and of course the lights went off. I pulled the switch and found that it apparently is substantially different in overall length from the original and I needed to remove completely one of the mounting nuts to position the switch closer to the pedal. Now with sufficient movement of the switch button the brake lights will shut off.

Also, thanks to @Stevehose & @deQuincey for their solutions.