93 K1100RS w/ABS I has a weird electrical problem.

[dieselyoda]

I did the engine in my 93 K1100RS and it runs most awesome. I had an ABS I problem that turned out to be the controller. Here is the thing, I can get everything to work but not at the same time.

My gauges work fine with fuse #1, the top fuse in but the ABS doesn't. If I pull fuse #1, the ABS works great but no gauges.

I can't find a wiring diagram that integrates the chassis electrics with the ABS circuitry. I am pretty certain that the wiring, grounds, etc. are all good but what I can't find is if there are any components, relays or whatever that are common to both circuits.

Short of tearing the bike down again and stripping the harnesses open to trace every wire, I don't know where else to look.

 

[98lee]

Check the voltages going to the ABS with fuse 1 out and then with it in.

The ABS is very voltage sensitive.

A dirty ignition switch can severely lower the voltage when a load is placed on it. I've had a switch drop the voltage from a fully charged battery to below 7 volts when the coils and guages were switched on (shouldn't drop at all). Cleaned switch, all is good.

 

[dieselyoda]

Check the voltages going to the ABS with fuse 1 out and then with it in.

The ABS is very voltage sensitive.

A dirty ignition switch can severely lower the voltage when a load is placed on it. I've had a switch drop the voltage from a fully charged battery to below 7 volts when the coils and guages were switched on (shouldn't drop at all). Cleaned switch, all is good.

OOOOOHHH, never even thought of that one.

Thanks for the start!!!

 

[dieselyoda]

Votage pretty damn good.

I have god voltage, 12.0 at the ABS and all the fuses with no change, fuse in or fuse out. Voltage drop from the ABS module and ignition switch is 0.02V.

 

[dieselyoda]

Getting into this mess...

I determined that pulling the Bulb Monitoring Unit from the system gives me both ABS and gauges but it's removed from the system. I was also able to find a jumper wire scotch-locked between bulb power and the power to the brake switches. Naturally, I couldn't figure out why the previous owner(s) would do that so I disconnected the jumper.

I put the BMU back in, fuse one back in, no ABS. Pull the BMU and leave fuse one still in, all seems to work.

I'm thinking I've got a bad BMU but no spare to try which means buying one somewhere to confirm that I'm right.

My big question is what does the BMU actually do? I took it out of the case thinking it was just a relay. It looks pretty damn electronic.

I've got another 6 months to figure this out so any help will be appreciated.

 

[98lee]

My big question is what does the BMU actually do? I took it out of the case thinking it was just a relay. It looks pretty damn electronic.

The bulb monitoring unit tells you whether your brake light, taillight, front (lever) brake switch, and rear (pedal) brake switch are all functioning properly. When first starting the bike, the warning light in the middle of the instrument cluster lights up red. After applying and releasing the front and rear brake separately, it senses the proper resistance in each curcuit and turns out the light. If an open curcuit is sensed (bad switch, bad bulb, bad socket connection) the light stays on.

 

[dieselyoda]

The bulb monitoring unit tells you whether your brake light, taillight, front (lever) brake switch, and rear (pedal) brake switch are all functioning properly. When first starting the bike, the warning light in the middle of the instrument cluster lights up red. After applying and releasing the front and rear brake separately, it senses the proper resistance in each curcuit and turns out the light. If an open curcuit is sensed (bad switch, bad bulb, bad socket connection) the light stays on.

Doesn't that go to something like a human appendix? Not sure why it's really there? I check my light on my other bikes routinely and when the bulb is out, that light doesn't work.

I can't test ride the bike as there is a foot of snow/ice on the ground and the tires REALLY need to be replaced. Best guess, what would happen if I left the BMU disconnected?

 

[98lee]

Doesn't that go to something like a human appendix? Not sure why it's really there? I check my light on my other bikes routinely and when the bulb is out, that light doesn't work.

I'm sure you don't check the lights EVERY time you stop for breakfast, gas, lunch, photo-op, gas, etc. during a high mileage day. This does. Bulbs and switches don't just fail BEFORE you leave your house. It's good to have.

 

[98lee]

I can't test ride the bike as there is a foot of snow/ice on the ground and the tires REALLY need to be replaced. Best guess, what would happen if I left the BMU disconnected?

You have been determining that the ABS is not functioning by doing the bulb check routine (apply and release front and rear brakes separately) and then going out and getting the bike up to at least 10 mph , correct?

 

[dieselyoda]

You have been determining that the ABS is not functioning by doing the bulb check routine (apply and release front and rear brakes separately) and then going out and getting the bike up to at least 10 mph , correct?

Most correct. Riding a very naked K1100RS around the block has my neighbours wondering if they live in a good neighborhood or the kind that runs chop shops.

If I leave the BMU out, I just loose that feature?

 

[98lee]

Yoda,

PM sent.

 

[dieselyoda]

My BMU guts.

Inside of my BMU, Look closely for the burnt straps.

 

[58058D]

If that is not 'the' problem.....certainly it is 'a' problem.....time for that new BMU.
I think congrats are in order for your persistance at finding the problem.

 

[dieselyoda]

Replacement BMU received, tried, dunno.

98Lee was gracious enough to lend me a BMU and send it to Canada. If it works, a quick fair payment and I could close my comments on this post.

First catch, parcel arrived in the hands of our Border Protection folks, torn open, handed to me and asked, "is this yours?" I said yes and needed to explain what it was, show them the bike and the other cooked part. I asked what the hassle was about and they said, "BMU, Bomb Making Unit". Thanks for using that acronym on the package Lee.

Without the BMU in the system, the ABS light and the Bulb light flash together. The ABS does work and my gauges work without the BMU. No codes in the ABS controller. I installed the BMU from Lee, the lights flash alternately. So I'm thinking I have a problem still.

Check the codes in the ABS, replacement BMU out or in, no codes! So I'm ready for a test ride. Problem: one foot of snow on the ground and -20C. New Problem, if I install a ski on the front tire and chains on the rear tire, would the ABS even be an issue?

Question, functioning ABS 1 and everything else working properly, do the red lights flash simultaneously or alternately?

 

[98lee]

Question, functioning ABS 1 and everything else working properly, do the red lights flash simultaneously or alternately?

I BELIEVE they flash simultaniously but not sure (the one ABS K75S that I own is not on the road yet).

I think if you go through the bulb check sequence, you will end up with only one light on.

Get up to over 4mph and the ABS will self check and shut off the other light (you might have to do the ABS reset after all the messing around that you've done).
http://www.ibmwr.org/ktech/abs-reset.shtml. I would use at least 30 seconds instead of 8.

Sensor clearances have been verified, correct?

 

[dieselyoda]

The ABS works fine with the BMU out of the system. As I mentioned, I found that jumper wire on the scotch-loks and the cooked BMU.

I can't practically get it up to any speed unless I'm wearing an air bag suit with our conditions. I suppose I could try but my next post might how you recover from injuries because I was stupid.

I guess at this point that after installing the BMU and I didn't get codes from the ABS, I am very optimistic but eager to confirm. Then again, I am pretty eager to cuddle up with a warm body and since my girlfriend is away, the cat will have to do.

 

[deilenberger]

IIRC (it's been a LONG time since I built the FYK's ABS wiring harness) the warning bulbs are wired in parallel - so they flash in unison. I think there are two of them just in case one burns out you'll have the other one to use.

 

[58058D]

It has been a long long while for me as well, but like Don, I do not ever remember them doing anything that was not together, no alternating on that bike, as I recall.

 

[dieselyoda]

Well, aren't you guys a pile of great news.

Looks like the next step is to put my fluorescent orange winter coveralls on, stick my expensive bright yellow skid lid on, open the shop door and aim for 10 miles an hour. The turn at the end of my driveway will be a challenge if the ABS doesn't work!

At least, when the neighbours complain about the loon that lives on their block, eventually they will find me. If I don't post anymore, I will let you know the results when I can walk and talk again. If I post pretty quick, expect some positive news.

 

[dieselyoda]

I can report that I put my blaze orange insulated coveralls on, got my beer drinking buddies to have a few more and convince me that this was a great idea to test the ABS in the dead of winter on an icy street on a motorcycle with bald tires. Warmed up the bike, opened the shop door, scooted down the driveway and I stopped! They worked!

When I start the bike, the red triangle light in the center of the instrument panel is on, no blinking. The ABS light is flashing. When I grab the front brake handle and press the rear brake pedal, both lights flash together. When I hit about 5-8 mph, both lights go out and everything appears to work.