Author Topic: Brake light always on (Read 2820 times)

Tin Tin · « **on:** February 18, 2015, 21:54:21 »

The story so far...

I've today noticed that my brake light stays on all the time. I have disconnected The front switch connector at the bars and removed the rear one completely and the light is still on. So from what I can see, there are no brake light connectors connected and activated yet my brake light is always on. Bulbs look fine and the bike has been working perfectly before today.

I've googled and searched forums but cannot see anything relevant.

Can you help?

V-Strom3 · « **Reply #1 on:** February 18, 2015, 23:15:31 »

Daft question - is bulb in the correct way around?

MartinW · « **Reply #2 on:** February 18, 2015, 23:22:08 »

I'm thinking the same as V-Strom3. The bulbs are keyed so they only fit one way, but I believe they will go in if "forced".

Does it look like the normal tail light comes on if you press the brake (although you might not be able to see it with the brake light portion stuck on)

Tin Tin · « **Reply #3 on:** February 18, 2015, 23:47:46 »

I've not changed anything skit cannot be a bulb failure or similar. The rear light just will not go off of fully on. I can only thing it's an electrical issue but that opens up a myriad of things to check and test

V-Strom3 · « **Reply #4 on:** February 18, 2015, 23:55:54 »

What year is the bike as the electrical system might be different.

greywolf · « **Reply #5 on:** February 18, 2015, 23:56:30 »

Your rear brake light switch needs to be adjusted so the switch body is lower. Find the spring wire with the coil in it on the rear brake pedal arm and follow it up to the switch.

Tin Tin · « **Reply #6 on:** February 18, 2015, 23:59:51 »

I thought this but I have removed it completely to rule it out, and disconnected the front switch. So at the moment it has no switches activating the brake light, yet it's still on?

greywolf · « **Reply #7 on:** February 19, 2015, 01:14:06 »

How did I miss that? Check the white wire with the black stripe for power against the black wire with a white stripe for earth. If W/B is live, something is crossed and giving it power. If not, the bulb connection in the socket has a problem. Do you have two bulbs or one?

Tin Tin · « **Reply #8 on:** February 19, 2015, 05:21:28 »

I've got two bulbs, both working correctly it seems. I'll try the wires tonight when I get home

Esmerelda · « **Reply #9 on:** February 19, 2015, 12:24:21 »

Bad earth maybe? Tail light finding it's Earth back through the brake light bulbs. Check out the connector for the back light unit.

Regards
Esme

Tin Tin · « **Reply #10 on:** February 23, 2015, 15:20:40 »

Well I have checked the wires and both the 'live' ones going to the rear tail light section are fully live all the time. Hitting the brakes doesn't change the power to the wires.

All seems intact - but I have no idea where to go next. Electrics are a different world to me, I just don't get it..

Any help much appreciated or it's off to the local dealer... Could it be a fuse somewhere? also how to you check the ground/earth wire?

greywolf · « **Reply #11 on:** February 23, 2015, 17:02:14 »

If the white/black wire is live with the brake light switches unplugged, it is connected somewhere it shouldn't be. One possibility is the black/white earth wire is not really earthed. Then the electrons from the gray wire could travel through the tail light filament and brake light filament to find earth. That would result in a series connection that would lower the brightness though and a bad earth for the brake light would also be a bad earth for the tail light as both use the same wire. If a bright light is always present, it's more likely the white wire with a black stripe is getting power from some location other than a disconnected brake light switch.

Tin Tin · « **Reply #12 on:** March 02, 2015, 12:16:05 »

OK so it went into the local garage P and H Crawley and they have said that it'll take them at least 8 hours to resolve.

which at £66 plus VAT per hour is ridiculous.

So I have no other choice but to try and resolve it myself. So in really simple terms (as I do not know anything about electrics) can someone try to explain tome how I test the wires please and what ones to test? I have a meter but it has AC DC and other settings?

Any help would be really appreciated as I cannot understand why in the morning it was fine then in the afternoon it was not..

greywolf · « **Reply #13 on:** March 02, 2015, 13:41:10 »

Maybe you can find another rider locally who has some experience. Solving electrical problems off site is very difficult, especially with those not familiar with tools and terminology. I wouldn't even want to try it. That time estimate will give you some idea of the possible complexity.

tallpaul · « **Reply #14 on:** March 02, 2015, 15:14:14 »

I'm not saying I'm going to find the answers but I've printed a copy of the wiring diagram for a wee ak7 (from the forum download page) on A3. I will try and highlight the wires for the brake light circuit and see if I can find where this rogue earth is coming from.

tallpaul · « **Reply #15 on:** March 02, 2015, 15:17:59 »

Another thought. I think I've seen posts regarding people having areas of the wiring harness chafing on the frame. Has this been considered?

Gassoon · « **Reply #16 on:** March 02, 2015, 15:39:30 »

As I understand it, the earthing is done through lots of wee black wires, not through the (alloy) frame parts anymore

You definitely need to use the D/C setting on the multimeter.

Did you do anything on the bike in the weeks before you noticed the issue? I'm thinking maybe the problem might have been there for a long time before you noticed? Is that possible?

If you can strip as many plastics off as possible and work your way from the switches, unplugging connectors to see if they have an effect (then re-plugging them after an inspection - maybe two have been mashed-together? Or somehow chafed together as Paul mentions [terrible problems with chafing, has Paul]) you should narrow down where the problem is.

Try phoning a few local auto-electricians , who have the skills, experience etc eg http://autoelectrical-crawley.co.uk/ele ... es/1251770 who are mobile as well...(tell them you'll strip all the panels , tank etc off the bike for them before they start!)

They might give you some pointers, at least. Try others on Yell!

MartinW · « **Reply #17 on:** March 02, 2015, 15:47:39 »

Quote from: "greywolf"

Maybe you can find another rider locally who has some experience.

+1 - There has to be someone local on the forum who will take a look for you.

So, come on, we have a member in need. Let's show what this site can achieve.

V-Strom3 · « **Reply #18 on:** March 02, 2015, 16:00:28 »

Quote from: "Tin Tin"

OK so it went into the local garage P and H Crawley and they have said that it'll take them at least 8 hours to resolve. which at £66 plus VAT per hour is ridiculous.

So I have no other choice but to try and resolve it myself. So in really simple terms (as I do not know anything about electrics) can someone try to explain tome how I test the wires please and what ones to test? I have a meter but it has AC DC and other settings?

Any help would be really appreciated as I cannot understand why in the morning it was fine then in the afternoon it was not..

I have a couple of standard rear tail/brake lights units as I have upgraded my k5 & k7 to led units.
If you want to try swapping them out, also with having me a January 2008 K7 650 ABS GT a side by side comparison of wiring might help.
I'm based in fareham (portsmouth).

alboy · « **Reply #19 on:** March 03, 2015, 14:39:34 »

It certainly sounds like a short somewhere, Sorry I can't physically help unless you fancy a trip to Ireland

. Electrical faults can be a real pain to diagnose, that is probably why the garage has quoted so much, if you are lucky you might find the fault in a few minutes (probably still charge for 8 hours!!) or a few hours. First of all I would trace the live wires back as far as you can go and see if there is any obvious damage on the insulation. Testing with a multimeter is easy if you know how but otherwise not.
When you say you removed the brake switches, did you actually unplug the wires from them?

Good luck

Al