Warning light

[BchrisL]

The brake light warning indicator is illuminating intermittently on my '03 RT. I checked the brake light and the running light, both are burning fine. The light will come on when the bike stopped in traffic during rush hour with a lot of idling and holding of the brakes with the aux fan running. It will then go out after I return to normal cruise after a few minutes.

 

I suspect the battery voltage is sagging during the idle time with the load of the anti-locks, and the aux cooling fan and fooling the computer into setting this warning light.

 

I think I should check the tension on the generator belt, as well as a check of the voltage of the system.

 

The battery is the original and is 6 years old, with almost 85K on it. It is near the end of its life span, and I did have a fuel pump failure earlier this month, which caused a lot of cranking loads on the battery over two days as I initially tried the restart the engine after the failure and subsequent troubleshooting of the fuel pump.

 

I am going to inspect/tighten the belt and do a load test on the battery, before I replace the brake/running lights which seem to be operating normally.

 

I welcome any additional thoughts you may have.

 

 

[KER]

i would check the reservoir levels in the abs unit, they are probably low. mine used to do this randomly, you need to pull the tank and check the fluid levels, they may just need to be topped off.

[Tony_K]

 

I suspect the battery voltage is sagging during the idle time with the load of the anti-locks, and the aux cooling fan and fooling the computer into setting this warning light.

 

The battery is the original and is 6 years old, with almost 85K on it. It is near the end of its life span,

 

Yup,

My bet is on that old battery. The load test will likely show in the very bottom of good or top of bad. 6 years... you had a winner there.

[T__]

Chris, a LOT depends on what the brake warning light is telling you & (IF) you still have brake power assist..

What brake light is flashing (one or both),, how fast is the brake light (or lights) flashing?

 

Give us more info..

 

Twisty

 

 

 

[BchrisL]

Chris, a LOT depends on what the brake warning light is telling you & (IF) you still have brake power assist..

What brake light is flashing (one or both),, how fast is the brake light (or lights) flashing?

 

Give us more info..

 

Twisty

Yes indeed I need to give you more information. When I posted last, only the warning light was coming on, not the ABS light, and the warning light was not flashing. I had full assist.

 

That was yesterday.

 

TODAY, as I roll into the subdivision down a long hill and apply brakes firmly with only the warning light on, the power assist stops and the ABS starts a rapid flash. I slowly cruise to my house with residual braking.

 

I guess I am going to pull off the tupperware and the tank tonight and check levels. I am hoping to find low fluid levels which I can top off , but that says to me there may be a leak if the pads are in good shape, and the fluid is low. I am still going to check the battery and the generator belt. It is old as well and may be loose.

 

 

[BchrisL]

i would check the reservoir levels in the abs unit, they are probably low. mine used to do this randomly, you need to pull the tank and check the fluid levels, they may just need to be topped off.

 

Did that...there was a little low. I will observe after I put it all back together.

 

 

I suspect the battery voltage is sagging during the idle time with the load of the anti-locks, and the aux cooling fan and fooling the computer into setting this warning light.

 

The battery is the original and is 6 years old, with almost 85K on it. It is near the end of its life span,

 

Yup,

My bet is on that old battery. The load test will likely show in the very bottom of good or top of bad. 6 years... you had a winner there.

 

I think I have the battery that was made Voltaire himself. It tests good on a load STILL!. After a minute of cranking with the tank off, the Fluke 27 in MIN/MAX mode, the voltage dipped only to 10.87V. I commute to work on this bike, and it is ridden some every day, year round (no snow, no ice). I think this is the key to long battery life. The belt is tight and looks good and supple. So my sagging voltage theory is blown out of the water.

 

I also checked the brake and running light...both are good. I replaced the brake lamp just to get rid of the extra bulb I had rattling around in my tool box from the last time it burned out years ago.

 

I don't know the problem is, I am tired, I missed the John Stewart show, and I am going to give up for tonight. The old Chevy will have to do tomorrow. (UGH!) ...and if this playlist loops around one more time I am going to go nuts.

 

[T__]

Chris, the warning light (only) on & not flashing & the brake assist still working is usually an indication the rear TAIL light bulb has issues.. In a lot of cases the bulb will look good or still seem to function but can have hair line crack in the filament (just replace the tail light bulb as a precaution..

 

On your loss of power assist,, I don’t know there.. How fast was the ABS light flashing? Was it flashing with or opposed to the warning light?

 

I guess start by verifying no sticking brake light switches in the front lever or brake pedal & that the I-ABS controller is full of fluid..

 

If you just can’t find anything yourself have your local BMW dealer pull the brake controller failure codes for you as that should point to what failed (or is failing)..

 

Twisty

 

[BchrisL]

Well I thought I had it solved, but no it still is there. If I hold the brakes for a time at a stoplight, or a series of slow stop and go, as in rush hour traffic that is creeping, I will get a WARNING LIGHT only. It will stay on for a while then go out after I ride for a while.

 

The tail bulbs have been replaced, but the original ones were fine. It looks like the battery is failing to hold voltage at idle, even though the load test looked good. I retested the battery tonight and it dips to 9.4V during a crank. I think I am going to feed it a battery, after six years.

[David R]

YES the voltage is dropping. Alt output is at its least at idle, your battery does not seem to have the capacity. 9.6 volts was always the lower limit for any battery. 5 years is a good life.

 

David

[NonComp]

Does the light go off when you give it some gas at idle?

[BchrisL]

Just an update. I replaced the battery. The problem is still there. It has a pattern. I can make it happen with a heavy application of the front brake. If the antilock system kicks in the unit will shut down and go to residual braking.

 

This is why I feel the need to get this thing fixed soon. I was going down a steep cobblestone street that was wet and the system shut down when it tried to antilock.

 

Now I mention this only as an afterthought because it has stuck in my mind for weeks now.

 

The very first time I saw the symptoms with the warning light, I though I smelled a wire smoking. I dismissed it because I was in heavy traffic and it could have been another vehicle nearby. But just maybe it was a wire on my bike comming from the antilock unit at the connector, and I have a loose connection causing a voltage drop at the unit. I hate opening the RT to work on it time after time, but I hate paying a shop several grand more, so I am going to snoop around the unit itself soon before I give up on this one and throw some money at it.

 

[T__]

Chris, yes do look around for burnt wiring or loose connections then check the fluid level in the controller.... If you just can’t find anything it might pay you to have your dealer at least pull the failure code(s) as that might point you to something such as low system voltage or faulty wheel sensor..

 

You might look real closely at the front wheel speed sensor wire & it’s routing as there were a few problems in that area..

 

Twisty

 

[BchrisL]

Chris, yes do look around for burnt wiring or loose connections then check the fluid level in the controller.... If you just can’t find anything it might pay you to have your dealer at least pull the failure code(s) as that might point you to something such as low system voltage or faulty wheel sensor..

 

You might look real closely at the front wheel speed sensor wire & it’s routing as there were a few problems in that area..

 

Twisty

 

Thanks for the reply.

 

My club (BMWBMW) is having a tech day Saturday. I hope to brainstorm with some of the wrenches there and maybe we can see something I am missing. They usually are able to diagnose most any thing with that group.

 

I am really not looking forward to taking this to a dealer, because I am sure they will shotgun the system and that is going to be expensive.

[AndyS]

.... It has a pattern. I can make it happen with a heavy application of the front brake. If the antilock system kicks in the unit will shut down and go to residual braking.

 

 

Once the Antilock disengages do the brakes re apply themselves?

These bikes have a phenomena where if the rear wheel locks it can let the brakes off with very frightening sensation of accelerating to your doom. Is this what you are experiencing?

Andy

[BchrisL]

.... It has a pattern. I can make it happen with a heavy application of the front brake. If the antilock system kicks in the unit will shut down and go to residual braking.

 

 

Once the Antilock disengages do the brakes re apply themselves?

These bikes have a phenomena where if the rear wheel locks it can let the brakes off with very frightening sensation of accelerating to your doom. Is this what you are experiencing?

Andy

 

They revert to residual braking which requires more pressure from the pedal/handlebar lever, but they still will stop the bike. No they do not reapply until you cut power and reboot the system.

 

BLEEDING ANTILOCKS