Ok then,

So, last couple of ride's I notice the ABS light won't cancel

also I notice the battery needs more charging than normal

Could the two be linked....ie low voltage on ageing battery (4yr old)

Happy Christmas all
Rod

Sorry to pop up again!
Low voltage can cause the ABS to fault. Have you tried to re set it?

No worries Mike,
 Glad to have the feedback

No, I didn't do a reset as I was thinking it was a low voltage problem,
and that won't resolve itself until I change out the battery

hence the Odyssey pc680 post

adios
Rod

DeRodster wrote:No worries Mike,
 Glad to have the feedback

No, I didn't do a reset as I was thinking it was a low voltage problem,
and that won't resolve itself until I change out the battery

hence the Odyssey pc680 post

adios
Rod

Hi Rod,
I've got a 680 non mine too. It is a power house of a battery and only the same weight as a large sidecar!
You'll be fine with that, what are they costing these days?

Mike.

Even if the battery is getting a bit tired with a low voltage then as soon as the bike is running the voltage will come up to a normal 13.8 ish volt charge. The K has a big enough alternator to achieve this even if you are running loads of electrical stuff off it. 
The battery on a bike serves only one main purpose and that is the start the engine, it is also a buffer on some bikes should they have a small alternator and many electrical loads, but that is not the case on a K.

Although a low battery fault shouldn't appear with a functional battery—given Bob T's description of the battery's relationship with a K's engine function, it nonetheless peskily does appear often enough that articles have been written and workarounds created such as in this artcle and this one.

Abandoning presumptions and resetting as Mike advises would seem a reasonable course of action.

Having thought more, I'm sure that if you can read the fault codes there is a code for low voltage...or is that just wishful thinking? No it isn't, I've found it!! See below.

• 1. front pressure modulator
  
  
• 2. rear pressure modulator
  
  
• 3. front wheel speed sensor
  
  
• 4. rear wheel speed sensor
  
  
• 5. battery voltage too low
  
  
• 6. ABS relay
  
  
• 7. ABS control unit
  
  
• 8. sensor gap front or rear, or other outside influence
  
  
• 9. unknown, but seems to exist
  
  
• 16. Failed plunger test, persistent
  
  

Here's the page.
http://www.largiader.com/abs/absfault.html

The momentary voltage drop caused when running the starter motor with a weak battery will cause the ABS to fault every time you start the bike even though the voltage when running goes to proper levels. 

You are going to get ABS low voltage faults as long as you try to run with a weak battery.  The way to check is to reset the fault, and then start the bike.  Without moving the bike, the fault will have returned.

You could try the following.

Ride off with the ABS lights flashing, and continue for a few miles. Stop, and immediately restart the bike. If the ABS lights are now extinguished, then it was a low battery fault.

Mike

"You are going to get ABS low voltage faults as long as you try to run with a weak battery."


I don't understand that statement as the ABS system would never know what the battery voltage is when the engine is running. At best the ABS computer can read system voltage, which might be low while starting, but will always be alternator voltage with the engine running. I have a voltmeter on my K.
I would suggest that the fault lies elsewhere.

BobT wrote:"You are going to get ABS low voltage faults as long as you try to run with a weak battery."


I don't understand that statement as the ABS system would never know what the battery voltage is when the engine is running. At best the ABS computer can read system voltage, which might be low while starting, but will always be alternator voltage with the engine running. I have a voltmeter on my K.
I would suggest that the fault lies elsewhere.

I think that's correct but I'd start looking elsewhere when a new battery is fitted then start reading fault codes. That should tell you where the problem is.
The system can obviously detect low voltage otherwise BMW wouldn't have built fault code 5 into the ECU. I've used these a few times and they've lead me straight to the problem.

Best way to diagnose is to ride for 20 minutes or so then turn the key off then back on while moving so the starter doesn't have any bearing if the light goes out then the battery voltage is the problem.
I have twice come across a fault that shows the same but is caused internally in the ABS unit which drains the battery over a 2 week period and shows as the low battery problem but not caused by a bad battery. It also does not reset easily.
Tosi Tabuki has fixed it twice and all is still OK.

I  had an issue with my ABS lights constantly flashing last year, and managed to trace the fault using the fault codes. 

It may be helpful to read my thread , albeit quite long winded, but if I can get mine working again and I am no sparky, then hopefully you can too.

Good luck 

Bob

Almost two years ago I had a problem with a low voltage fault on my K75RT ABS system.  With a fully charged battery and a faulty ignition switch I would get an intermittent voltage drop across the switch that dropped the electrical system voltage to around 7.5v when the switch was on, and to almost zero when the starter was activated.  The voltage was so low that it couldn't weld the starter relay contacts.

Every time I got the fault I had to do a manual reset.  It wasn't until I cleaned the switch that the fault stopped occurring.

Thanks All,
Interesting feedback and it raises a few more questions

How do I read the fault codes, do I need an oscilloscope, or a multimeter or some hi-tech equipment ???

I am still tending towards an end of life battery...more from experience in the electronic field than any direct expertise with my K.  Time will tell I guess

I see also that I definitely need to be careful with the +pos battery contact, so as not to creat a short

and then there is the matter of the "small wire" taht connects the battery box to the chassis...where might I locate that I wonder. is it an integral part of the loom or ?

I think it's going to be a busy winter in the garage !!!

Rod

That is a totally separate wire about 100mm long with a 6mm eye at each end. One end under the starter bolt and the other end under one of the bolts holding the amplifier to the battery cradle. If you remove the amplifier use some heat-sink paste to reseat it

You can read the codes with a 12v LED connected to the three socket diagnostic plug under the seat on the right hand side of the frame. 

Here is some information on troubleshooting ABS faults:

http://www.motobrick.com/index.php?topic=538.0

Brilliant
Thanks for that
I did see that 3pn socket and wondered what is was for

I'll make up the tester unit and give it a go later

adios
Rod

Not wanting to hijack the thread, but it is ABS related 

Today I finished swapping my alternator for a 50 amp unit, plus a new motobatt battery. 

Started up fine with the charging light glowing slightly until she had run for few minutes then it went out. Reading 13.92 volts so pleased with that. but...

ABS light did not go out and reading the fault code, I got seven flashes , the ABS brain .

Bugger...

Reset the ABS just in case , but no luck .  Read the code, seven flashes .

Luckily I had a spare Brain off e bay so swapped it over , and all good again.

Hope you get yours fixed DeRodster

Bob

my battery also died last week, replaced it with a 32ah lawnmower battery for 50 euro, perfect. my ABS lights wouldn't go out either, did the trick above by earthing the centre pin in the plug, worked first go! this forum is brilliant for hints and tips, keep em coming. thanks