K11 Owners Group

Sonu · Posted: Sat Jul 26, 2008 9:33 pm Post subject: Brake light inop

Friends,

My brake light is not working.

I checked the bulb and it does not look blown, resistance measured close to zero so it must be OK. All fuses seem to be OK.

With the power lead (grey & yellow wire) disconnected, I measure 0.2V at the connector with the ignition turned on (bike in neutral on center stand). With either the front or rear brake applied the voltage drops to zero volts. What the heck? I'd think that the voltage should go from nearly zero to 12 volts on application of either brake.

License plate light is working normally.

Any ideas?

Sanjiv
_________________
1997 K1100LT "Ziggy" _GarminGPS_Corbin saddle_K Guards _Hyperlights_Fog lights_Eastern Beaver Relays_Cee Bailey_4"speakers_Michelin PR4's_MoS2_Spiegler lines_TPMS_VDO

Flying Duck · Posted: Sat Jul 26, 2008 11:25 pm Post subject:

What is the BMU (Bulb Monitor Uint/triangle light) doing after yout hit both front and rear brakes?
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Sonu · Posted: Sun Jul 27, 2008 12:32 am Post subject:

Hi Drake,

Thanks for the quick response.

I've never opened the relay box below the tank. I think I located the BMU (called Lamp Control Unit in the service manual Pg 61. Cool

. Am I holding the right thing in the picture?

What is it supposed to do? Right now when I press either brake I do not hear any clicks or other noises within the BMU. I'm afraid I need a bit more instruction.

As a digression, I was surprised to find two connectors (one white, one black at the bottom of the picture above) that are not hooked up to anything. They certainly don't mate with each other. Are these for optional accessories? My bike came "fully loaded" so what the heck are these for?

Thanks

Sanjiv
_________________
1997 K1100LT "Ziggy" _GarminGPS_Corbin saddle_K Guards _Hyperlights_Fog lights_Eastern Beaver Relays_Cee Bailey_4"speakers_Michelin PR4's_MoS2_Spiegler lines_TPMS_VDO

Jim · Posted: Sun Jul 27, 2008 9:29 am Post subject: brake light

Sanjiv - don't know what the extra connectors are for - I've got them too - they've nothing to do with your current problem.
_________________
Jim
1997 K1100LTSE 94,000 - still has gremlins!
1995 R100RT Classic 16,650 crashed - repaired!
1992 K75RTP 46,000

"We shall not all die, but we shall all be changed."

Flying Duck · Posted: Sun Jul 27, 2008 9:38 am Post subject:

Black - radio and other aftermarket options.

White - Alarm system.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Sonu · Posted: Sun Jul 27, 2008 9:47 am Post subject:

Thanks Guys,

So back to the current problem. How do I diagnose the brake light inop situation? What's the BMU supposed to be doing? Does it need replacement? How do I confirm its the problem?

Sanjiv
_________________
1997 K1100LT "Ziggy" _GarminGPS_Corbin saddle_K Guards _Hyperlights_Fog lights_Eastern Beaver Relays_Cee Bailey_4"speakers_Michelin PR4's_MoS2_Spiegler lines_TPMS_VDO

Flying Duck · Posted: Sun Jul 27, 2008 9:55 am Post subject:

I just asked what your BMU was doing - you didn't need to dig into the relay box.

The BMU makes sure your lighting is working. When you start the bike the "triangle" light stays on solidly until you have applied both front and rear brakes. The BMU makes sure your brake switches are both working nad that the bulb is good. This is a safety feature because if you ride around with a non-working brake light chances are you'll eventually get run over.

Does the brake light go on when the front brake is applied? Rear brake applied? Or does it not work for either?
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Sonu · Posted: Sun Jul 27, 2008 10:38 am Post subject:

Hi Drake,

Sorry for the digression. I put the bike back together.

The BMU seems to be working fine. Solid red when bike is first turned on. Once both brakes are applied the light goes off.

Tail light on all the time.

Brake light does not come on when either front or rear brake is applied.

Brake light bulb confirmed to be OK. Voltage at +ve lead swings from 0.2V to 0V when either front or rear brake is applied.

Sanjiv
_________________
1997 K1100LT "Ziggy" _GarminGPS_Corbin saddle_K Guards _Hyperlights_Fog lights_Eastern Beaver Relays_Cee Bailey_4"speakers_Michelin PR4's_MoS2_Spiegler lines_TPMS_VDO

Flying Duck · Posted: Sun Jul 27, 2008 12:16 pm Post subject:

I'd try a NEW bulb first. 1156 is the bulb size.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Sonu · Posted: Sun Jul 27, 2008 12:24 pm Post subject:

Hi Drake,

I'm going out anyway so I'll pick up a bulb but I highly doubt that the bulb is the issue.

I swapped the (+)ve lead between the brake light and the tail light and the brake light bulb (now powered by the tail light voltage) turned on just fine.

Sanjiv
_________________
1997 K1100LT "Ziggy" _GarminGPS_Corbin saddle_K Guards _Hyperlights_Fog lights_Eastern Beaver Relays_Cee Bailey_4"speakers_Michelin PR4's_MoS2_Spiegler lines_TPMS_VDO

Flying Duck · Posted: Sun Jul 27, 2008 12:29 pm Post subject:

Yeah, bulb does sound good.

Remove the tail light lens. Take out the two screws that hold the wiring harness conneector. Check terminals for corrosion and clean them anyway - WD40 & wire brush.

Check to see what happens there with your voltmeter.

If you brake light isn't working then your BMU should keep the triangle light on. But check the connector first.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Sonu · Posted: Sun Jul 27, 2008 3:55 pm Post subject:

Flying Duck · Posted: Sun Jul 27, 2008 5:15 pm Post subject:

Double check the fuse #1. BMW fuses can sometimes go bad but still look good.

After that I'd pull out the Clymer manual, look at the wiring diagram and chase the wire back to the relay box. Check for continuity from the relay box to the tail.

If the wire is good then maybe it's the BMU. I don't know what magic occurs insdie there so don't know how to diagnose it - but I do find it fishy that it's going out when the brake light isn't going on.

I can sell you a good used one if you want to try that.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Sonu · Posted: Sun Jul 27, 2008 5:38 pm Post subject:

Problem solved Very Happy

It was a poor contact at Fuse #1
The fuse itself was fine. It measured 0.04 ohm (same as a new fuse). Simply removing the fuse and putting it back a couple of times cleaned up the contact.

I cant thank you guys enough. You've sure saved me a lot of $$ over the years.

Sanjiv
_________________
1997 K1100LT "Ziggy" _GarminGPS_Corbin saddle_K Guards _Hyperlights_Fog lights_Eastern Beaver Relays_Cee Bailey_4"speakers_Michelin PR4's_MoS2_Spiegler lines_TPMS_VDO

Flying Duck · Posted: Sun Jul 27, 2008 5:45 pm Post subject:

Sometimes the fuse receptor terminals get pushed back - you can push them back out from inside the relay box.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE