DIY: E32/E34 Brake Light Circuit Warning Light Repair

[shogun]

E34/E32 BRAKE LIGHT CIRCUIT - CHECK CONTROL FAULT MESSAGE REPAIR - By Master E32FAN

"My 1992 735 iL had intermittent troubles with BRAKE LIGHT CIRCUIT. It persisted with three different CCM modules. So, it's time to replace the Brake Light Switch, right? Well, maybe not!"
The complete story for a free repair on the shogun website in my signature, click fixes>>brakes>>> Check control fault message repair

In case it is not working on IE11, use google chrome for the time being, working on that problem now to solve it.

[shogun]

That is the easiest solution, if it works. If not, you have to clean the switch http://www.nmia.com/~dgnrg/page_25.htm
Some comments from a German forum (google translated) :
The idea/ solution is very elegant. The switch does meanwhile cost abt. EURO 40. It can be explained as imagined by a fireplace. The fireplace has a lot of soot on the walls of the fireplace. The solution - burn more wood or hardwood - the temperature rises and the soot is burnt too. The procedure with the switch is apparently similar. The burnt area shifts outwards and the contact is clean again.

Contacts need some current load , so that the growing oxide burns . It is a self-cleaning effect, which just does not work with too low load. It is a small spark at the contact, brushing away the 'dirt' ...

[632 Regal]

I'm going to clean the bulbs and sockets, sporadic problem here and I don't think it's getting any worse. Now to find my Stabilant 22A...

[632 Regal]

Sure enough one socket connector was oxidized, the other bulbs contact was melted flat from heat. Will see if I get the infamous warning again. Stabilant 22 seems to break down the corrosion chemically.

[MicahO]

When I got the Touring, it was showing a Brake Light Circuit error. The PO had mentioned that it happened from time to time and he felt it was something that was wonky with the trailer wiring. I saw the error on the display and didn't actually look at the rear of the car.

About a week after delivery I was going to go get the car inspected and wisely had my son look at the back of the car for brake lights first. NO BRAKE LIGHTS!

I found a 10w bulb on one side, and a crappy 26w no-name bulb in the other side. doh I replaced those with new, proper 21w bulbs and still nothing. So I tested the brake light switch and found that it was inop.

The repair instructions are great, but I got a new one for $7 or $8 down at Autozone. Inspection: Passed! cheers

Interestingly, I had also been getting an erroneous low oil warning. Those went away when I corrected the brake light issues, so I did not have to replace the oil level sensor!

[shogun]

Sure enough one socket connector was oxidized, the other bulbs contact was melted flat from heat. Will see if I get the infamous warning again. Stabilant 22 seems to break down the corrosion chemically.

Stabilant is good, but this repair as described refers to the contact surfaces of the brake light switch itself above the brake pedal. To get to it with Stabilant, you would have to remove it and disassemble it. Therefore the idea to 'burn' the contact surfaces of the switch via the pin of the CCM plug, much easier.

@MicahO
if you find a solution with the erroneous low oil level warning, let ius know. My buddy has the same problem, we already changed CCM modules several times, made new plug connections near the oil level switch, no success.
Maybe that is the same problem with the contacts inside the oil level switch.
Oil level signal pin on the CCM is #26 on X18 http://www.bimmerboard.com/forums/posts/275437

[632 Regal]

Stabilant is good, but this repair as described refers to the contact surfaces of the brake light switch itself above the brake pedal. To get to it with Stabilant, you would have to remove it and disassemble it. Therefore the idea to 'burn' the contact surfaces of the switch via the pin of the CCM plug, much easier.


After reading in the links it mentioned the brake light circuit triggers from any deviation in resistance. This is why I decided to check the bulbs before replacing the brake switch. It used to trigger when it gets colder more often than warm weather so we will see if it triggers in the next few days.

[632 Regal]

Well that was short lived... need a new switch.

[bennyg]

This is far more impressive than what I did to fix the warnings on my other E34 - the multi meter found they were just caused by rubbish quality solder failing in the eBay quarity clear indicator tail lights.

[632 Regal]

This is far more impressive than what I did to fix the warnings on my other E34 - the multi meter found they were just caused by rubbish quality solder failing in the eBay quarity clear indicator tail lights.

I had those clears on Nikka, let them go with the car. Sockets so fussy could take 10 minutes to get them to make a circuit which would work until the next "brake light out" warning.