Brake lights permanently on

[minesapint]

Yesterday had what may be my last drive of the year before winter lay up. (Drive into the Yorkshire Dales with a pie & a pint for lunch, fantastic)
When starting the car in garage noticed the "check" light didn't come on, (press brake pedal to cancel) then whilst on drive saw my brake lights were permanently on, & were throughout the journey.
Does anyone know exactly what the cause of this is & the fix?
Cheers

[Grrrmachine]

Probably a loose/sticky light switch above the brake pedal.

[Jamesy]

Had the same problem, found brake light switch was the cause.

[milescook]

With your hand, pull the brake pedal up if it budges, and get someone to watch your brake lights. If they go off your pedal needs adjusting, to dial out the slack that's causing it to drop and activate the switch. If so, there's lots of threads about how to do it better than I could explain, but essentially a bar runs from your pedal mechanism to the sever piston behind the glovebox. Near the pedal you can slacken off a nut and turn the bar to tighten. It is a bitch to get to!

[minesapint]

Lack of use......

Normally you'd not be far off the mark, but with this brilliant summer we've had I've been out nearly every day & covered around 1700 mls.
Interestingly when getting the car up & running in June after years of being "laid up", the check system worked first time & has until yesterday.
Cheers anyway

[minesapint]

Probably a loose/sticky light switch above the brake pedal.

I understand how that makes the brake lights come on, but why is the "check" light not on also?
I've always assumed the "check light system" is there to check brake pressure upon start up before commencing a journey. That's hydraulic pressure, not a switch on the brake pedal.

[jmc330i]

The check light simply tells you if the brake light bulbs are working - the check light goes out once the pedal has been depressed and brake light bulbs come on.

[Grrrmachine]

That's hydraulic pressure, not a switch on the brake pedal.

Hah! E30s are nowhere near that complex. The brake LIGHT test measures resistance across the brake bulbs, nothing more.

[Brianmoooore]

The initial cause of brake lights staying on, on RH drive cars, is the brake pull rod needing adjusting, as milescook says. If the car is left in this condition for any length of time though, the brake light switch itself is also likely to give up and need replacing.
The bulb monitoring system on E30s is on the primitive side by today's standards, and needs the bulb in question to be powered up before it can be tested, which is why the warning LED stays on until the pedal is pressed. More modern systems test the bulbs with a much lower current than their normal running current, which doesn't cause the bulbs to visibly light up.

[minesapint]

Thanks for that guys, very informative, I'll investigate & report.
Cheers

[Laith]

I had this the other day after I adjusted my brake pedal height.

It was too low to press the brake light switch anymore when I released the pedal.

The solution was to push the brake pedal in whilst pulling out the red 'sleeve' of the brake light switch (gently without breaking the switch) towards the front of the car so that when the brake pedal was released, it would press the red sleeve therefore activating the switch.

Best thing is to take that dash lower panel off and have a proper look - it will all make sense then.

[minesapint]

Had a look this afternoon.
A simple task of adjusting the brake switch, which is threaded for adjustment, 17mm spanner to release the locking nut & move the switch forward. It only needed 2mm of adjustment & job sorted.



Still looking brand new under there, not bad for 28 yrs old. (that's the car not me!)



Thanks for the help, Cheers

[Brianmoooore]

Brake switch is only adjustable on older models, and if it was set correctly at the factory, shouldn't need to be adjusted now. Pull rod (visible behind clutch cylinder in second pic.) is probably what you should have been adjusting.

[Brianmoooore]

That's hydraulic pressure, not a switch on the brake pedal.

Hah! E30s are nowhere near that complex. The brake LIGHT test measures resistance across the brake bulbs, nothing more.

Not even that complex! Later BMWs do a resistance check - E30s just check that sufficient current is drawn by each bulb when lit.

[minesapint]

Brake switch is only adjustable on older models, and if it was set correctly at the factory, shouldn't need to be adjusted now. Pull rod (visible behind clutch cylinder in second pic.) is probably what you should have been adjusting.

Do you think I should do that then, there is no play in the brake pedal at all.

[Brianmoooore]

There won't be now that you've moved the switch down. Back the switch off, then see if there's any play.