1990 K100LT ABS fault.

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krankshaft
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1990 K100LT ABS fault.

Postby krankshaft » Thu Dec 30, 2021 11:57 am

Hi, guys
My ABS light has been flashing for a long time and this is the first chance I've had to try anything more than just
earthing the fault plug and holding the ABS switch for 10 seconds, which has not cleared the fault.
It started a while back. I was at a roundabout and my back wheel was sitting on a wet, slippery tramline, and the wheel spun very slightly when I let out the clutch, instantly, the ABS fault lamp began to flash and it has flashed ever since.
As I said, I tried to clear the fault the usual way, but to no avail. Today, I replaced the ABS sensor on the back wheel with a used one from Motorworks and checked the sensor clearances on both wheels and they seem ok.
Has anyone any ideas? Maybe the brain itself is faulty?
Thanks for any suggestions.
Ride safe
Jim

krankshaft
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Re: 1990 K100LT ABS fault.

Postby krankshaft » Fri Dec 31, 2021 12:48 pm

Sorry to reply to my own querie, but I remember a few weeks ago someone had removed a complete ABS system and was looking for a new home. If it is still available, I would be very interested. I really think my ABS is faulty.
Thanks for any ideas
Ride free
Jim

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Re: 1990 K100LT ABS fault.

Postby stanthomas » Fri Dec 31, 2021 7:14 pm

This seems to be the goto guy for ABS faults : http://bmwk10075abs1fix.web.fc2.com/

I pulled the ABS off my K100RS 16v 'cos the test suggested the control box was faulty and, when I opened it up, it had corrosion on the board which according to website above means it can't be repaired. If you need any bits, other than the controller, I have them in a box.

krankshaft
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Re: 1990 K100LT ABS fault.

Postby krankshaft » Sat Jan 01, 2022 12:17 am

Thanks, Stan
That's an interesting site. I will go through things a bit more thoroughly. I haven't had much time recently and this job has been put off as the brakes work fine without the ABS, but I'll be happy to have everything working.
Cheers again
Ride safe
Jim

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Jaythro
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Re: 1990 K100LT ABS fault.

Postby Jaythro » Sat Jan 01, 2022 10:09 am

When you push the ABS button do the lights stop flashing ??

If not the switches have a bad habit of the wire corroding off over time

And finally do the lights start flashing immediately on pressing the starter or as soon as you power on the ignition ?
"Put your Ass on a motorcycle and ride with an attitude and the "Grim Reaper" will ride in your shadow!"

Islandmagee in case you're interested?

krankshaft
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Re: 1990 K100LT ABS fault.

Postby krankshaft » Sat Jan 01, 2022 10:54 am

Hi, jaythro
The ABS light starts flashing alone as soon as key is turned and stops flashing i.e. glows uninterupted,when ABS
switch is pressed.

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Jaythro
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Re: 1990 K100LT ABS fault.

Postby Jaythro » Sat Jan 01, 2022 1:12 pm

Worth trying to read the codes to be honest

https://www.k100-forum.com/t5192-homema ... ors-tester
It takes a second or two for the images to load
"Put your Ass on a motorcycle and ride with an attitude and the "Grim Reaper" will ride in your shadow!"

Islandmagee in case you're interested?

krankshaft
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Re: 1990 K100LT ABS fault.

Postby krankshaft » Sat Jan 01, 2022 11:00 pm

Had some time today, but as the sun was shining, went out for a spin instead.
When I got home, I switched the bike off and restarted it to observe the ABS lights and the starter
relay jammed on. I quickly disconnected the earth cable and took the bodywork off to get the tank off.
I removed the relay and checked for continuity and it was definitely stuck closed. I reconnected the connector from the starter button (but not the power cables) and pressed the starter button several times and the relay was completely behaving itself again. I tried it about 50 times and it was working perfectly, but I've ordered a new one and will carry an allen key in my pocket for the next week to isolate the battery if it happens again as I have to use the bike to go to work.on monday.
In he meantime, I'll set up the test to count the ABS fault codes. Thanks
Ride safe
Jim

krankshaft
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Re: 1990 K100LT ABS fault.

Postby krankshaft » Tue Jan 11, 2022 9:42 pm

I know this is getting a bit off topic, but the new starter relay came today and I installed it and it too is jamming closed.
Am I missing something? After I mounted and connected the relay, I tested it a few times and it jammed closed and I had to disconnect the earth cable to stop the starter motor. I carefully removed it and took it to the bench and tested the power leads with a continuity tester and there was a short circuit between the cables. I then tapped the relay with a screwdriver and tested again and it was open circuit.
Apart from a faulty relay, is therer any other explanation?
Thanks
Jim

krankshaft
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Re: 1990 K100LT ABS fault.

Postby krankshaft » Tue Jan 11, 2022 10:17 pm

Just an additional point. On the bench, using a 12 volt power supply, on both relays, I could not get them to stick closed. On the bike, however, they stuck when the engine started. Could it be that when my engine starts, the alternator puts out a voltage spike that welds the contact points of the relay closed. Has anyone heard of this? That woulkd be an alternator/regulator issue?
Any thoughts welcome. Thanks.
Ride safe, it’s getting cold!

Mike D
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Re: 1990 K100LT ABS fault.

Postby Mike D » Wed Jan 12, 2022 1:18 am

A failing battery (or high resistance joint i) can cause the relay contacts to weld shut. It's a common fault on K bikes.

Mike


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