Page 1 of 2 1 2 LastLast
Results 1 to 15 of 18

Thread: Need help on R50/5 charging issue

  1. #1

    Need help on R50/5 charging issue

    I just bough an R50/5. It starts and runs well. But when lights and turn signal is engaged while riding it drains the battery so quickly!!
    But when riding with NO lights and turn signal battery is fine.
    I presume there is a problem with the charging system (dont know which part and what's causing this). What would be the cause of this problem? Any help is greatly appreciated...
    Attached Images Attached Images

  2. #2
    Registered User 80092's Avatar
    Join Date
    Jan 2014
    Location
    Stroudsburg, Pa
    Posts
    159
    For starters Check with a voltage meter the amount of voltage to the battery when running . Lights off then on and compare . The problem could be a relay or brushes, be sure to have a good ground and check other related wires. Can't hurt to go to Snowbum's site for more detail.
    Nice Bike BTW !
    Peter Murray
    Stroudsburg, Pa.
    IBA 359
    2014 RTW, 73 R75/5

  3. #3
    P Monk
    Join Date
    May 2005
    Location
    Orange, Texas
    Posts
    847

    all you need to know

    http://www.motoelekt.com/goodstuff.htm

    This is like the Bible for Airhead electrical problems. All the answers are in there.
    P. Monk
    74 R90/6 (the Black Hole), 2011 R1200RT.

  4. #4
    Registered User lmo1131's Avatar
    Join Date
    Jan 2010
    Location
    Pismo Beach, CA
    Posts
    3,987
    1) When you insert the "key" and push it all the way down, does the red generator warning light come on? Location 3 below
    2) And does it go out when the engine is running?
    3) Do you know, reliably, how old the battery is?



    Ditto what Peter said. I always liked that color: Federweise, I think?
    "It is what you discover, after you know it all, that counts." _ John Wooden
    Lew Morris
    1973 R75/5 - original owner
    1963 Dnepr

  5. #5
    Quote Originally Posted by lmo1131 View Post
    1) When you insert the "key" and push it all the way down, does the red generator warning light come on? Location 3 below
    2) And does it go out when the engine is running?
    3) Do you know, reliably, how old the battery is?



    Ditto what Peter said. I always liked that color: Federweise, I think?
    1.) when key is inserted and pushed all the way down, the generator warning lights is "NOT ON"
    2.) NO light when engine is running
    3.) I just bought a new Yuasa battery.

    QUESTION:

    1.) What would be the possible cause of this issue? and what parts is involved? and how to test the parts if defective...i.e. diode, voltage regulator, rotor, stator..etc?
    2.) How big is this job/repair in scale of 1 - 10?


    BTW thanks for complimenting the bike. I really like the color of it...

    Regards,

  6. #6
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    20,558
    As Lew was pointing out, that red light is pretty critical. It's actually part of the charging circuit...the book from Motorrad Elektrik shows that. If it's burned out, then current from the battery is not getting to the windings of the alternator to start the electro-magnet. Without that, you won't get any charging.

    Seems like the first thing you need to do is get into the headlight and carefully retrieve the bulb and check it...possibly all that needs to be done is replace it.

    Down the road, if you're interested, there is an electrical mod that can be done to insert a resistor in the wiring harness which will allow for charging even if the bulb is burned out. That's really for a situation on the road so you can still get home, because you really do want to see the light and get feedback from it.

    I'd say it's a 2/3 out of 10 type of job...depends on the general skill set. But be sure and ask questions about getting things apart as the /5s might have a few tricky steps. And if you're not getting charging (have you started it and measured the voltage at the battery...it should rise to near 14v at say 3500 RPM), the more you ride it, you will be pulling the battery down and eventually get stuck and/or possibly ruin the battery.

    Let us know what you find out.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  7. #7
    Thanks for the reply...

    So if it's just the red charging bulb, can this be repalced? or do I have to buy a complete headlight assembley? I hope buld can be replaced...thanks again

  8. #8
    The circuit is battery to ignition to kill switch to bulb to voltage regulator to 12v+ (hot) alternator brush to rotor through rotor to ground brush to ground. Usually the problem is not the bulb. Usually the problem is either severely worn brushes or an open circuit (broken wire) in the windings of the rotor.

    Yes - the bulb can be replaced if necessary. But first use the bike's built in circuit tester.

    Disconnect the negative (ground) battery cable.
    Remove the front cover from the engine.
    Hook the battery ground cable back up.
    Identify the two wires to the brushes on the alternator.
    Brown is ground - the other wire is +12v

    Key on (pushed down)
    Kill switch on.
    Unplug the +12v wire and ground it against the engine block.


    Did the light come on? If so you have confirmed a brush or rotor failure.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  9. #9
    So glad I joined BMW MOA forum....you GUYS are the best and a great source of knowledge..

    I will follow the procedures and will post an update.

    Till my next post...

    Ron

  10. #10
    Registered User lmo1131's Avatar
    Join Date
    Jan 2010
    Location
    Pismo Beach, CA
    Posts
    3,987
    Key on (pushed down)
    Kill switch on. ...
    Just so you don't fret about it, there is no "kill switch" on the /5. This won't affect Paul's procedure.

    What you will see when you remove the headlight. This is a later /5 equipped with fuses (black cylindrical shapes with green wire @ 4:00 position).
    Depending on your build date, your bike may not have them.



    Below: What you will see when you get passed all the spaghetti.
    The bulb holders are a friction fit; just pull on then. A slight twisting action might be needed.
    If you ever need to remove the instrument, the two tall "nuts" are removed, the crossbar is removed, and the instrument is free to come out from the top.


    "It is what you discover, after you know it all, that counts." _ John Wooden
    Lew Morris
    1973 R75/5 - original owner
    1963 Dnepr

  11. #11
    Quote Originally Posted by PGlaves View Post
    The circuit is battery to ignition to kill switch to bulb to voltage regulator to 12v+ (hot) alternator brush to rotor through rotor to ground brush to ground. Usually the problem is not the bulb. Usually the problem is either severely worn brushes or an open circuit (broken wire) in the windings of the rotor.

    Yes - the bulb can be replaced if necessary. But first use the bike's built in circuit tester.

    Disconnect the negative (ground) battery cable.
    Remove the front cover from the engine.
    Hook the battery ground cable back up.
    Identify the two wires to the brushes on the alternator.
    Brown is ground - the other wire is +12v

    Key on (pushed down)
    Kill switch on.
    Unplug the +12v wire and ground it against the engine block.


    Did the light come on? If so you have confirmed a brush or rotor failure.
    Hi Paul....yet another question, when you say "ground it against the engine block"....what I understand is to tap the red +12v wire to the engine block? Am I correct? I just wanted to make sure. Sorry for this dumb questions as this is really new to me and my first old bmw R50 bike...thanks again.

  12. #12
    Quote Originally Posted by ron1200rt View Post
    Hi Paul....yet another question, when you say "ground it against the engine block"....what I understand is to tap the red +12v wire to the engine block? Am I correct? I just wanted to make sure. Sorry for this dumb questions as this is really new to me and my first old bmw R50 bike...thanks again.
    Yes - touch it to a clean metal spot on the block. From the end of that wire the normal flow is through the hot brush, through the rotor, through the ground brush to ground. Touching the wire on the block to ground it just bypasses the brushes and the rotor. It thus tests the whole circuit upstream to the battery.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  13. #13
    I got it...now I am about to remove the front engine cover but do have another newbie question....can front cover be remove without removing the gas tank? or its a must to remove the gas tank before I can remove front engine cover??

  14. #14
    rabid reader dbrick's Avatar
    Join Date
    Apr 2003
    Location
    Santa Cruz CA
    Posts
    2,337
    Make sure you disconnect the battery before removing the front cover. There are connections under there that carry juice, and can easily short to ground when the cover comes off. Doing so does Bad Things.
    David Brick
    Santa Cruz CA
    2007 R1200R

  15. #15
    Per instructions above.. I just need to disconnect the ground baterry cable...and the positive should remain connected correct? Also should I remove the gas tank to be able to remove the front engine cover??

    Thanks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •