BMW K bikes (Bricks)

You are not connected. Please login or register

View previous topic View next topic Go down  Message [Page 1 of 1]


1Back to top Go down   Starter and load shed relay Empty Starter and load shed relay on Sun 29 Mar 2009 - 8:37

Crazy Frog

Crazy Frog
admin
admin
As it is very difficult for most people to follow the full electrical schematic, I made this simpler one about the starter relay and load shed relay.
The function of the load shed relay is to disable lights and accessories to give the maximum power from the battery to the starter.
This may help you to understand how it works as well as troubleshooting a starter not turning.

The way that the load shed relay works is confusing but in fact cleaver.
The relay coil is fed with the positive(+) from the ignition switch on one side and from the ground(-) coming from the starter on the other side(the ground is passing through the inductor of the starter motor). when you push on the starter button, this ground will be switched to positive and the load shed relay coil will then be fed by a positive(+) on both sides (This is like not having power). At this point, the load shed relay will be released and the lights and accessories will go off.

Note: if the gear box is in neutral, the starter button is fed from the digital gear display(power passing through a diode). If not, it is fed by the clutch switch.

THIS IS WHY PEOPLE ARE TALKING ABOUT THE GROUND COMING FROM THE STARTER. If you have a bad starter, your lights, flasher,horn and fan may not be working as the load shed relay coil doesnt get its negative. Smile

Note: When the battery is low, DO NOT TRY TO START THE BIKE. You may end up burning the starter relay (a $130 mistake)

Starter and load shed relay Starte12

    

2Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay on Thu 5 Mar 2015 - 10:07

MikeisonTV

MikeisonTV
Silver member
Silver member
Thank for this. So I understand a little more about troubleshooting these relays....will the starter attempt to fire the bike, if the relay is faulty? Or not engage at all?

If the load shed relay is faulty, will the bike turn the starter, but not fire the bike?

Thoughts on testing the integrity of them? will using a test light and the battery work or damage it?


__________________________________________________
Yep! I'm flipping through the air....that ain't good.
    

3Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay on Thu 5 Mar 2015 - 12:06

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Thanks for posting the diagram, Bert.  Now I finally understand what is going on with the load shed relay.  Didn't realize that it is energized closed to power the circuits it controls and goes normally open when the starter is energized.

One question, though.  Is there supposed to be a ground drawn on the other side of the starter relay coil?


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

4Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay on Thu 5 Mar 2015 - 21:22

robmack

robmack
Life time member
Life time member
Point Seven Five,

No, the other side of the starter relay coil does not go to ground directly. Bert has exercised artistic license in his drawing and eliminated huge sections of the bike's electrical system for simplicity's sake, including the ICU and ECU. The other side of the coil goes to the ICU. Below 700RPM, the starter coil gets its ground connection through the ICU. Above 700, the ICU prevents the starter relay from engaging for safety.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

5Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay on Thu 5 Mar 2015 - 23:21

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Cool, info burned to whatever memory I have left.  Still, it would be handy to show the ECU contact with a note about the 700rpm logic.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

6Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay on Fri 6 Mar 2015 - 0:34

92KK 84WW Olaf

92KK 84WW Olaf
Life time member
Life time member
@Point-Seven-five wrote:Cool, info burned to whatever memory I have left.  Still, it would be handy to show the ECU contact with a note about the 700rpm logic.

Due to average age of K riders certain aspects are committed to memory to force us to remember.......that 700rpm or 710rpm is important.....


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 102,50 miles
1983 K100RS 0011171 Fricka 606 29,495 miles Damn K Pox Its a Bat outta Hell No 34,600 miles
    

7Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay on Fri 6 Mar 2015 - 8:31

kioolt

kioolt
Silver member
Silver member
@MikeisonTV wrote:Thank for this. So I understand a little more about troubleshooting these relays....will the starter attempt to fire the bike, if the relay is faulty? Or not engage at all?  

It may or it may not.  It depends on what is wrong with it.


If the load shed relay is faulty, will the bike turn the starter, but not fire the bike?

The starter and the bike will fire fine even if you have a bad load shed relay.  The load shed relay has NOTHING to do with the bike starting or running.  It's there to turn off accessories when starting the bike.  

Thoughts on testing the integrity of them? will using a test light and the battery work or damage it?

I would test them while completely installed with a voltmeter on the output side of the contact. 


__________________________________________________
2004 R1150RT 186,800 miles 
1991 K100LT 128,700 miles
1982 R100RT 106,900 miles
Total 422,400 BMW miles

AMA,BMWRA,BMWMOA


The cheapest thing on a BMW is the nut that connects the handlebars to the seat.
    

8Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay on Fri 6 Mar 2015 - 9:41

RicK G

RicK G
VIP
VIP
"Due to average age of K riders certain aspects are committed to memory to force us to remember.......that 700rpm or 710rpm is important....."

To be precise 711rpm.....no I don't know and I doubt BMW knows either.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

9Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay on Fri 6 Mar 2015 - 17:46

MikeisonTV

MikeisonTV
Silver member
Silver member
Thanks k100LT


__________________________________________________
Yep! I'm flipping through the air....that ain't good.
    

View previous topic View next topic Back to top  Message [Page 1 of 1]

Permissions in this forum:
You cannot reply to topics in this forum