• Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password.

    If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?

1993 K75S Dead Electric System

J

JSCORTINO

Guest
I have purchased a new to me 93 k75s .When i purchased the bike it neede a few repairs but the bike ran and started . The only indication orf a problem was the ABS light and the hazard warning light was on.
I replaced both the leaking brake lines front and rear and found a bad rear brake light switch which i replaced. We bled the system and all the brakes worked great.Reset the ABS computer to attempt to shut off the warning lights. Started the bike and took it for a test ride with no problems other than the Abs light starteed blinking again. I parked the bike and left it over night the next day whent to take it for a ride I turn the key and everything is dead except the clock. Here is what I checked
1. Battery at 13 volts but drops drastically if ignition switch is turned on
2. checked ignition switch with ohmeter seems to work properly
3. checked all fuses
4.checked ground connections
5. checked relays and unplugged ABS system no change
Any body have any ideas
Thanks,
Jim
 
It sounds very much like:

a. A very discharged battery - maybe drained down overnight by a load.
or
b. A bad battery

My best guess is b. bad battery.

I would try to charge the battery and see what happens.
 
Paul,
It is a brand new battery,where to look next?
Jim
 
Jim,

Brand-new batteries fail sometimes - not too often, I agree - but I agree with Paul that you should assess its condition before you go further. If the battery is bad and you think it's good, the rest of your troubleshooting will be for naught. It's a lot easier to make sure now, rather than have to backtrack later.

The symptoms you describe are those shown by a voltage drop from a battery that is not fully charged. That might be because a) the battery is good, but is not fully charged, or b) the battery is defective and incapable of holding a charge. To determine which is the case, disconnect the battery from the rest of the bike's electrical system, either by removing it or just disconnecting one or both of the battery cables. Then charge the battery fully.

The first test assesses what happens to the battery voltage when it addresses a load. Connect a headlight bulb across the fully-charged battery terminals. If after charging, the battery cannot light the bulb or the battery voltage drops significantly when the bulb is connected, the battery is defective because it won't take a charge; the battery should be replaced. If, on the other hand, the bulb lights brightly and the voltage doesn't drop or only drops a little (no more than half a volt) while the bulb is connected, then the battery has taken a charge.

The second test addresses whether the battery can hold a charge. Charge the battery, let the battery sit overnight, and then test it again. If it's significantly less strong the next day, then the battery is again defective because it is incapable of holding a charge. If it passes both tests, then the battery is indeed OK and the electrical system's problem is elsewhere.

With a known good battery (not just an "I believe it's OK because it's new" one), reinstall the battery in the bike and measure the current draw with everything turned off. Only the clock should be drawing current then, and it should draw a very small amount - I'd guess <10 ma. A higher draw tells you that there is a current leak somewhere in the bike's electrical system - worn or crushed insulation on a power-carrying wire within the main wiring harness near the steering head and under a too-tight zip tie is common in K-bikes.
 
Where are you testing the battery voltage? Right on the two battery terminals? Or on the battery cables? Or some other location?

If on the terminals, the battery is probably at fault. Not properly charged or more likely bad. I've seen several bad "new" batteries. One guy bought a new battery from the bike store and it had less than a half cup of acid in the entire battery.


:dance:dance:dance
 
Battery at 13 volts but drops drastically if ignition switch is turned on

This is a textbook open call battery fault. A common way aging batteries to die, but not unheard of with new batteries (manufacture defect.) How far is "drastically"? Under 10 volts?
 
Bad batteries

Well it turns out both the old and new battery were bad ,I have ordered a new one .Hopefully this solvbes the issue.
Thanks for the help
Jim
 
Back
Top