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1Back to top Go down   Starter and load shed relay Empty Starter and load shed relay Sun Mar 29, 2009 9:37 am

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 Thu Mar 05, 2015 11:07 am

MikeisonTV

MikeisonTV
Silver member
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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 Thu Mar 05, 2015 1:06 pm

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


Past:
1988 K100RS SE
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 Thu Mar 05, 2015 10:22 pm

robmack

robmack
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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 Fri Mar 06, 2015 12:21 am

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


Past:
1988 K100RS SE
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 Fri Mar 06, 2015 1:34 am

92KK 84WW Olaf

avatar
Life time member
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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 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 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 40,490 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

7Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay Fri Mar 06, 2015 9:31 am

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 Fri Mar 06, 2015 10:41 am

RicK G

RicK G
admin
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"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 2004 K1200GT 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

9Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay Fri Mar 06, 2015 6:46 pm

MikeisonTV

MikeisonTV
Silver member
Silver member
Thanks k100LT


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

nigel6527

nigel6527
New member
New member
Hi All,

I was wondering if any one has experienced this. I have stripped down my K1100lt which is currently a cafe racer fitted with a Acewell clock and a bep 3.0. The bike ran fine last year and I also fitted a Motogadget M-lock which operated as it should. Now this winter the bike has been pulled apart and the frame and engine painted. I have stripped out all the ABS loom as it is no longer present on the bike.

So the frame has gone on to the engine fixed at the front mounting points only, I have put the loom back in, connected the clocks and all the other wires and check all my earths which are the main harness earth, Acewell clock water sender earth, motogadget earth these all go to the frame earth point and an earth from the mototronic unit which goes to the gearbox at the moment. . Now, when I activate the m-lock all I am getting on the clock is a red oil light! no horn indicators nothing, no start button.

I then pulled the loom again went and traced all the wiring to check if I has snipped a wire by mistake and all seems to be ok apart from 2 wires. Blue brown wire coming from the frame to Engine plug, this is not connected to anything and I believe it went to an ABS plug. Then I also have a white/brown wire from the main instrument plug which is the 4L warning light wire. This is also not connected to anything. Neither of these I think will cause the issue I am having.

I would point out that I have had the clocks work once then they turned off again. The engine currently has no fluids in it as I am basically trying to test the electrics.

Can anyone shed any light have I missed anything here? I have power on the positive and neutral terminals on the starter relay also. Any help would be greatly received. Thank you. NIGEL

    

11Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay Sat Dec 18, 2021 12:18 pm

davemadsen

davemadsen
Silver member
Silver member
I have symptoms that seem to indicate a issue with the load shed relay - as well as symptoms that are NOT consistent with a bad load shed relay.

Recent history: the bike ran fine and as part of maintenance I replaced the voltage rectifier since the brushes were out of spec. I installed the new voltage rectifier and the bike starts fine and the voltage across the battery terminals indicate the bike is charging (13.8v).

Problem: in completing this work I have lost lights, turn indicators, horn, hazard lights, and temperature gauge - classic load shed relay activity. BUT, these items do NOT work before the bike is started. Normally, when the ignition is turned to the ON position, these accessories work until the starter button is pressed at which time the load shed relay shunts the power to these items. The bike runs fine. In summary, the lights, turn indicators horn, hazard lights, and temperature gauge should work with the ignition ON and prior to the starter button pressed - but they don’t. 

The fuses are good.

I am perplexed inasmuch as everything worked fine until I removed the ECU, battery and voltage rectifier. Note, I did not remove the alternator to complete this work.

What am I missing?

Dave


__________________________________________________
Dave
    

12Back to top Go down   Starter and load shed relay Empty Relay Sat Dec 18, 2021 12:41 pm

daveyson

daveyson
Life time member
Life time member
Try swapping the load shed relay with the horn relay.


Your symptoms are consistent with a permanently open load shed relay. When you turn the key on,  you should hear a click from the load shed relay.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

13Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay Sat Dec 18, 2021 12:54 pm

Laitch

Laitch
Life time member
Life time member
davemadsen wrote:What am I missing?
You're missing the opportunity to smack the load shed relay with a screwdriver handle, unless you didn't want to admit trying that. Smile


__________________________________________________
1995 K75 81,000 miles
Starter and load shed relay Usa-lo10
    

14Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay Sat Dec 18, 2021 1:29 pm

davemadsen

davemadsen
Silver member
Silver member
Problem resolved. I whacked (technical term) the load shed relay with no satisfaction so I whacked the horn relay and the lights came back on - Eureka! 

Is this a one-off incident do I need to plan on replacing the relay? Also, I noticed the load shed relay has a fifth pin. So while it was recommended to swap the horn relay (4-pin) with the load shed relay (5-pin), are they in fact interchangeable?

The pins and sockets of all relays appear corrosion free and still coated with the dielectric grease I applied during previous maintenance sessions.


__________________________________________________
Dave
    

15Back to top Go down   Starter and load shed relay Empty Relay Sat Dec 18, 2021 1:35 pm

daveyson

daveyson
Life time member
Life time member
The five pin relay is the fuel relay. There are quite a few drawings which label the relays wrong. 

Top left is fuel relay, top middle is load shed relay, top right is horn relay. You can think of the horn relay as a spare for the load shed relay, but then horn won't work if it's failed.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

16Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay Sat Dec 18, 2021 2:25 pm

davemadsen

davemadsen
Silver member
Silver member
Ahhh, the Clymer’s manual has the relays mislabeled. I see now I had whacked the load shed relay.

Thanks you so much for following up and providing the clarification.


__________________________________________________
Dave
    

17Back to top Go down   Starter and load shed relay Empty Relays Sat Dec 18, 2021 2:37 pm

daveyson

daveyson
Life time member
Life time member
No worries. Another quick way to verify it, for example, remove the top right relay (horn relay) then the horn won't work. Remove the fuel relay, then the fuel pump won't work, etc.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

18Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay Sun Dec 19, 2021 3:19 am

Laitch

Laitch
Life time member
Life time member
davemadsen wrote:Is this a one-off incident do I need to plan on replacing the relay?
You'll probably be motivated to replace it after the second or third time you've smacked it. Smile


__________________________________________________
1995 K75 81,000 miles
Starter and load shed relay Usa-lo10
    

19Back to top Go down   Starter and load shed relay Empty Re: Starter and load shed relay Sun Dec 19, 2021 11:04 am

Dai

Dai
Life time member
Life time member
BEFORE YOU GO OUT AND BUY NEW RELAYS: the ones on the K-series are DIN-A standard which means they have the switched power (pin 30) and coil power (pin 86) swapped over compared to the later (and off-the-shelf) DIN-B series. Secondly, despite having five pins, the five-pin relays are not changeover relays. See this:

https://www.k100-forum.com/t15966-relays-relays-relays-types-and-substitution


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

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