Check panel brake light warning

[jlevie]

As an FYI...

My restoration project car had an annoying habit of having the brake light warning led light up in the Check Panel (and the Flashing CHECK in the cluster) about a third of the time. I'd already replaced all the brake light bulbs with plated base Osrams, cleaned all of the bulb sockets, and the connectors. BTW: a brass bristle shotgun cleaning brush works like a champ. Get one that has little to no wire sticking out or trim it back to get deep into the sockets.

In retrospect it should have been obvious, but I didn't figure it out for a while. The cause was the brake light switch. While it was good enough to operate the brake lights it had just enough resistance to trigger the warning led some of the time. A simple check for this is to disconnect the switch, turn on the ignition, and use a wire to simulate the switch closing. If you do that multiple times with no warning led, replace the switch.

[36brua]

Thanks for the heads up. ya never know what's next with an E30 electrical system

[TimKninja]

It was actually a recall by BMW at one point, The brake light switch seized on my first E30 (85 325e). Couldn't figure out why the light wasn't going off.

[audiquattrot]

good to know. had this issue in all of my E30s past/present.

[Urnatha]

As an FYI...

My restoration project car had an annoying habit of having the brake light warning led light up in the Check Panel (and the Flashing CHECK in the cluster) about a third of the time. I'd already replaced all the brake light bulbs with plated base Osrams, cleaned all of the bulb sockets, and the connectors. BTW: a brass bristle shotgun cleaning brush works like a champ. Get one that has little to no wire sticking out or trim it back to get deep into the sockets.

In retrospect it should have been obvious, but I didn't figure it out for a while. The cause was the brake light switch. While it was good enough to operate the brake led tubes it had just enough resistance to trigger the warning led some of the time. A simple check for this is to disconnect the switch, turn on the ignition, and use a wire to simulate the switch closing. If you do that multiple times with no warning led, replace the switch.

These LED brake lights are creating problem for me. They light for some time and then gets off. What could be the reason?

[jlevie]

If you are talking about the brake warning LED in the Check Panel, understanding how the LED works may help.

Each of the monitored light circuits has reed relay wrapped in a coil of wire that is a part of the circuit. If sufficient current flow exists through the coil the reed relay closes. So anything that reduces current flow though the circuit will turn on the warning LED. Possible causes include aged bulbs, corrosion in the bulb sockets/connectors, bad fuse, damaged wiring, or bad switch.

[mcskibadee1]

stupid question I'm sure but where is the brake light switch?

[jlevie]

The brake light switch is on a bracket over the pedal arm.

[StereoInstaller1]

Another common cause of this issue is corroded connectors on the check panel diode pack.

Personally, having completely solved the issue on well over 2 dozen cars by simply cleaning the contacts (the bulb base thing is a myth) that is the first thing I do, and generally, it cures it.

Luke

[jlevie]

APersonally, having completely solved the issue on well over 2 dozen cars by simply cleaning the contacts (the bulb base thing is a myth) that is the first thing I do, and generally, it cures it.

I disagree because I've seen cases where all that was necessary to fix a persistent brake warning light issue was to replace the brass based bulbs (that were obviously corroded) with plated base bulbs.

[xcx4x]

As an FYI...

My restoration project car had an annoying habit of having the brake light warning led light up in the Check Panel (and the Flashing CHECK in the cluster) about a third of the time. I'd already replaced all the brake light bulbs with plated base Osrams, cleaned all of the bulb sockets, and the connectors. BTW: a brass bristle shotgun cleaning brush works like a champ. Get one that has little to no wire sticking out or trim it back to get deep into the sockets.

In retrospect it should have been obvious, but I didn't figure it out for a while. The cause was the brake light switch. While it was good enough to operate the brake lights it had just enough resistance to trigger the warning led some of the time. A simple check for this is to disconnect the switch, turn on the ignition, and use a wire to simulate the switch closing. If you do that multiple times with no warning led, replace the switch.

How do I "disconnect the switch"?
Where do I stick the wire to simulate the switch closing?

Thanks.

edit: found a youtube video

https://www.youtube.com/watch?v=9VHpF0rTx_M

[Aleman]

Seeing as how it sucks to work under the dash, I skipped the test and just replaced the brake light switch with a new genuine BMW part for $25. The part looks a little different from the original, so it's safe to say they probably improved its design at some point. Anyway, the brake light warning doesn't come on any more. Thanks, Jim, for pointing me in the right direction to look at the brake light switch.