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RE: ABS Light
- From: "Clive Liddell" <cliddell@xxxxxxxxxx>
- Date: Mon, 2 Apr 2007 15:03:05 +0200
- Subject: RE: ABS Light
Michael and Tom,
Further to your reply, I would recommend anyone having this problem to go to
the IBMWR pages and under Oilhead Tech Pages read Mick's writeup "ABS-II Low
Voltage Fault Modification" carefully.
He has automated his "solution" with an additional relay etc. I have gone
partly the same route but have not automated mine. Following the very clear
illustrated instructions in the writeup I have solved all ABS problems
during cold starts on my R850R and the R1100RT awaits an convenient
opportunity to be done.
Where I have differed is that I have cut the relevant wire in the connector
and joined and brought out the two ends to a "push to open", "normally
closed" press button switch. Now, when the ABS lights start alternating, I
just press the button and this resets the ABS and they start flashing
Since the engine is usually already running at this stage it avoids having
to stop it and restart just to get the ABS reset and in any case it is
usually only the first cold start of the day that results in a fault...
I'm not an expert on blinking codes of ABS lights, so someone else may have
a better diagnosis, but...
Early Oilhead with ABS light on is pretty common. I'm gonna guess it's the
battery. If your start pulls a few too many amps on a weak battery, the
voltage goes down to the rest of the system momentarily during the starting
process. This kicks on the ABS light. This early version of ABS had no
tolerance for low voltage.
The temporary solution is to warm up the bike and let the battery charge a
little by riding around (assuming your brakes still work) then shut it down
and quickly restart. It should start without the ABS light coming back on.
If it does, it indicates a weak battery. Replace it because it'll just
keep getting worse.
DON'T TRY THIS AT HOME:
I had a battery go down during a trip in colorado and I friction-started my
'99 RT. This method starts the bike without the help of the starter motor,
so no low voltage unless your battery is really dead.
Get the bike rolling with key on, drop the clutch in 4th gear, then pull
clutch in when the motor starts.
If you've already started the bike and want to get the ABS light off, keep
rolling, (any speed above 10 mph) pull in clutch, turn off ignition, turn on
ignition, let clutch out momentarily to start engine. (This is completely
unsafe if there is any traffic around, so use good judgement.)
Warning: Use 4th or 5th gear to do this. Low gears will cause the rear
wheel to skid when you drop the clutch. So long as the bike still starts
normally, I'd just do this procedure at 30 to 50 mph after the bike has
warmed up. With practice, you can do it really quickly, barely losing
I don't think the early ABS needs the bike to be at a standstill to reboot.
If it does, you have to pull over and restart the bike with the starter when
it's warmed up...starter will pull less on the battery than it does with a
cold engine, but it's not as good as friction-start, battery wise.
Both ways are band-aids, but they work. Won't cure the problem, it will
just get your ABS light off until you can get a new battery.
My bike turned over very hard one morning while I was touring. ABS light
went on. I used this method at 50 or so to get the light off. Next day, in
Gunnison, CO, it wouldn't start at all, so we pushed it and I used this
method to start the bike cold...lots of work. I used it at gas stops etc
all day. One learns to park pointing down hill.
I was on my way to Top o the Rockies rally. When I got there, I bought a
battery and installed it at the motel. Next day, I brought the old one back
to the dealer for recycling. No more problems.
Do you recall that last battery thread? It was mostly about the new Gel/AGM
batteries, but there was some mention of Wesco and Panasonic batteries.
The Panasonics seem to work OK, but the Wesco doesn't (or didn't in the old
days) have the cranking power to keep this ABS light from going on. Many
people with your vintage bike have seen the ABS light problem with brand new
Wesco batteries. I don't know if Wesco has fixed this problem or not. BMW
AGM batteries and Oddesy batteries work well. I have a friend who liked his
Panasonic battery on a '96 RT.
I don't think you'll find any BMW lead acid batteries around anymore.
They're all AGM now. Special charger needed for major charging, but I think
the small trickle chargers still work for topping them up occasionally in
Your problem could have some other cause, but I doubt it. I'll bow to
superior technical people in an instant on this. The slightly weak
battery/ABS light problem is really common on early Oilheads though.
I'm remembering that there was an update to the ABS system beginning with
'98 models that made ABS less volt-sensitive. Even in my '99 RT, the light
would go on during a start in really cold weather.
To my knowledge, you can't update the ABS system to the '98 spec easily.
It would involve replacing the ABS unit completely...big job for small,
Hope this helps,