"Brake-light failed" warning LED comes on

Post Fri Jun 30, 2006 11:29 am

I have the common problem of an intermittently illuminating Ã¢â‚¬Å“brake-light failedÃ¢â‚¬a LED in the check panel of my 1992 325 cabrio. The brakes lights themselves are always fine.

They have new BMW bulbs and I have thoroughly cleaned the connectors and bulb sockets and sprayed with switch cleaning fluid but no joy.

Someone on the site raised the possibility of the pedal switch causing a problem but I can't see how that would be. Surely the warning device must measure the resistance of the circuit to the bulbs after the brake pedal switch or it would always return failure ?

The car has had a tow bar fitted and I'm wondering whether the interference with the cables has raised their resistance.

Any comments on any of this?

Andrew

Post Fri Jun 30, 2006 11:52 am

I had this once and it was when i went over a bump the light come on i just closed the holders up a little

Post Fri Jun 30, 2006 12:22 pm

This happens to me every now and then, it is always prompted by activating the indicator.....??

Peejay.

Post Fri Jun 30, 2006 12:24 pm

Hmm. I think your smiley says it all....

Well I did ask for any thoughts!

Andy

Post Fri Jun 30, 2006 3:19 pm

peejay wrote:This happens to me every now and then, it is always prompted by activating the indicator.....??

Peejay.

Thank God, someone else with my exact problem! Every time I indicate left, never right, I get the light coming up. Its only every now and again, normallly towards the end of a journey, as if the fucking thing can tell!!

Any solutions please help me solve this incredibly annoying fault!

Post Fri Jun 30, 2006 3:29 pm

Well it's good to have the E30 zone so you can know you're not just going mad.

The way to cure all of this I guess is to find where the connection from the sensor circuit links into the brake light circuit and wire a clean new connection from there directly to the brake light bulbs.

Does any one know?

Post Fri Jun 30, 2006 5:14 pm

Disconnect the socket for the tow bar as it change the resistance of the unit (or just give the socket a good clean) and then check the wiring through the boot bulkhead to make sure its not rubbing on the bodywork.
Then clean the earth for the rear lights (

can't remember where it is though, think it may be under the back seat) can someone else confirm that ?

Post Fri Jun 30, 2006 5:18 pm

The check control circuit is in the left hand side of the boot, near the arial.
Thats could be where the earth for the unit is

Post Fri Jun 30, 2006 9:56 pm

If the switch gives a resistive connection, even for a short period, then the current through the brake light circuit will be reduced. If this is sufficiently reduced the lamp failure module will interpret this as a blown lamp.

Post Fri Jun 30, 2006 10:06 pm

Yes of course; see the point. I' think I'll try flooding that with switch cleaning fluid also prior to a swap.

many thanks

Post Fri Jun 30, 2006 10:07 pm

i have the same problem, except mine is permanent and not the brake light! mine shows as the number plate light not working, but they are?? ive tried different bulbs, i suppose it comes down to the module in the boot?

Post Fri Jun 30, 2006 10:14 pm

One thing I was considering is soldering the bulb in and/or bridging across the large round connector on the light cluster to remove those sources of possible resistance.

Post Fri Jun 30, 2006 10:23 pm

AndrewL wrote:One thing I was considering is soldering the bulb in and/or bridging across the large round connector on the light cluster to remove those sources of possible resistance.

Nothing on a BMW requires bodging like this. Identify the fault and repair it properly!

Post Fri Jun 30, 2006 10:54 pm

Had similar symptoms on my '87 320iSE, where it started blowing the brake lights fuse and tripping the warning lamp which I soon realised was occurring after going over bumps. Initially, I 'bodge' cured it by fitting progressively bigger fuses (going from the original 8.5A up to 35A!!). It would last longer (a week or two) with the bigger fuses presumably because they could absorb the surge of the temporary short. The car initially had tow-bar wiring, which I removed since someone had cut off the tow bar with an angle grinder anyway (!), and I took the rear lamps module apart but couldn't see anything wrong with it (not much in it, apart from four coils/inductors), checked the wiring as far as I could, and tried operating the circuit without the rear lamp units in place. Now I'm left with it constantly blowing any fuse put in it, even with the car standing still - aargh!

I guess I'm probably going to have to re-wire the circuit to cure the fault...

Does anyone know of a particular area where the brake light wiring is likely to be shorting?

Cheers,
James, E. Kent

Post Fri Jun 30, 2006 11:02 pm

320iSE wrote:
Does anyone know of a particular area where the brake light wiring is likely to be shorting?

Cheers,
James, E. Kent

There's no common place for the brake light wiring to short out.
Have a good look where tow bar wiring was connected in.
If the fuse blows every time you push the brake pedal, than try pulling the plugs off the lamp check module in the boot. This will narrow the problem down to in front of, or behind the module.
There's a good chance you have destroyed the entire car body wiring loom by your stupidity in fitting larger fuses.

Post Fri Jun 30, 2006 11:10 pm

this light occasionally shows on mine too when i first start the car but after dadding the brake pedal it goes out and stays out i thought it may be the brake light switch on the pedal .

Post Fri Jun 30, 2006 11:24 pm

alane wrote:this light occasionally shows on mine too when i first start the car but after dadding the brake pedal it goes out and stays out i thought it may be the brake light switch on the pedal .

It's supposed to do that!!

Post Fri Jun 30, 2006 11:38 pm

oh ok thanks

Post Sat Jul 15, 2006 12:25 am

Well, I finally got my brake lights going again on my '87 320iSE, by rewiring the system with a good old 'back to basics' hook-up direct from rear lamps via brake light switch and direct to battery live. For the life of me I couldn't trace the fault with the original circuit - seems it was shorting at the fuse box somewhere (still blowing fuses after disconnection of the rear lamps and brake-check control unit in the boot) but it's such a spaghetti in the fusebox I didn't bother to delve in further. Only snag is I'm still left with the Brake Lights warning LED showing on the rear view mirror panel and the flashing "!" indicator pulsating away in the instruments pod. Nothing a bit of black insulating tape can't cure

(I may get around to disconnecting the bulb that does the "!" thing...)

James,
E. Kent