brake failure

[texbid]

i have an interesting gremlin. the bike rides great, starts on the first try after sitting for 3 months on a battery tender.

I ride with no issues for a while and then on decelerations with with a closed throttle the brake failure light turns on and i loose servo brakes.

the battery is not BMW, and i have an autocom installed. (dont use it, should just take it off)

anbody with similar problems?

any fixes?

[snowprick]

Where are you getting the power for the Autocom? If it is from the brake light circuit then that could be the problem.

[zax1150]

first choice would be to check the batt voltage,
ignition off :min 12+volts
ignition on : No less than 11.37V

does the abs telltale flash with the failure?

if you have access to someone with an BMW interface check the system fault log......

[texbid]

i am getting the autocom power from the battery terminals.

and yes, the brake failure light flashes.

the battery is an after market unit. I have heard that the whole system is very sensitive to battery voltage??

has anyone seen this happen??

[snowprick]

i am getting the autocom power from the battery terminals.

and yes, the brake failure light flashes.

the battery is an after market unit. I have heard that the whole system is very sensitive to battery voltage??

has anyone seen this happen??

Autocom should not be the problem in this case.

[MikeCam]

Well, it could be a weak battery that fails to take a minimum charge after running awhile. The ABS will fail if the battery voltage falls below a minimum - don't recall level but it's fairly high in the 12.5-12.8v range.

It could also be the electronics of the ABS control unit undergoing a sporadic failure - at deceleration the fluid pressures are read, the wheel spin rates are compared, the weight shift is calculated, and the ABS/servo system adjusts as required. If any part of that circuit is faulty, the ABS faults start.

You can test the battery. Under basic operating load, it still needs to provide 12.5 volts or more. If not, replace and see what happens.

The fault codes will relay information about the ABS unit.

(But if the ABS passes system self-test at start-up I'd guess it's a bad cell in the battery or just a weak battery.)

[texbid]

thanks. i will start with te battery replacemnt. it had gone dead once and the problem started appearing ofter that.

should have known

[hank]

Before doing anything major replace the stop/tail bulb with a new one and see what happens.

This may sound stupid, but I have heard of dodgy bulbs causing ABS / brake warning to show and cause the servo to stop working.


Hope this helps

Hank.

[Rockster1150]

i have an interesting gremlin. the bike rides great, starts on the first try after sitting for 3 months on a battery tender.

I ride with no issues for a while and then on decelerations with with a closed throttle the brake failure light turns on and i loose servo brakes.

the battery is not BMW, and i have an autocom installed. (dont use it, should just take it off)

anbody with similar problems?

any fixes?

Don't want to be a dampner sort of guy, but when my revs dropped as stated above was when my Servo/ABS would intermittantly dissapear and the fault light would Flash, nil servo brakes. 1st thing I did was replace the battery, no fix here, then had the BMW dealer check the Fault Codes. Bingo. This was the 1st time I had the ABS unit replaced. Been there all again after 8k km, 2nd time I just started the bike and got the fault flashes, skipped work that morning and rode directly to the dealer for a fault check. Brakes returned upon the way so I was reasonerably safe doing this. - Another new unit fitted.