1985 K100 no running lights have brake light.

[Kckershovel]

Hello, my first post and it might be a tough one. I just bought an 1985 K100 I’m trying to bring back from the dead. I have tested lots of things and here is where I’m at.


I have the bike running. I have to jump the starter to crank it but it runs finally. I have power to starter solenoid small wires when button is pushed but doesn’t engage starter. I’m guessing just a bad solenoid. No big deal.


 My real problem is that I have no running lights!


If I ground starter no lights tap on starter no lights swapped flasher and load shed relay no lights. Relay clicks when I plug in and out of harness. I can jumper power to one side of load shed and I get lights. I jumper power to other side of load shed and starter engages.


Now the hillbilly in me just wants to pull the load shed relay and jumper the lights to work. The bmw is smarter than me and reading about importance or said relay wants me to fix it correctly. So anyone have any ideas?

[Kckershovel]

Also I just noticed my fan doesn’t kick on but the fan works when hooked to power and my temp warning light comes on. That’s how I know the fan isn’t coming on when it’s supposed to.

[Kckershovel]

Sorry to everyone reading I’m still working on it and adding to my post as I go. Seems the load shed relay powers fuse 7 that powers the cooling fan. If I jumper the load shed relay the fan works so I’m back to the load shed relay.

[Laitch]

. . . so I’m back to the load shed relay.

Knock the relay with a screwdriver handle, adjustable wrench or brass knuckles. That might get it to comply temporarily. Clean its terminals. Do the same to the starter relay because its contacts might be temporarily seized. Diagrams with labels and locations are in the K100 troubleshooting guide in the Repair Guidance section.

Check the wiring to the coolant temperature sensor, clean its mounting threads, test it for its range of function according to the procedure in the troubleshooting guide. That's a key component for activating the fan at the correct temperature.

[Kckershovel]

Thank you for the reply and I have done all things mentioned. The problem is with the load shed relay circuit.  I don’t have power to fuse #7 unless I remove the load shed relay and run a jumper wire.


Question for everyone.... I have been looking and I can’t find what the load shed connector should test with key on kill switch in run but bike not running. As it stands I have two slots with power and two without. If I jumper power to the green wires I get power to fuse #7 and everything works as it should. If I jumper power to the black wire the starter trues to turn. I only did that once in frustration to just see what would happen.


Can anyone tell me what I should see at the load shed plug?

[Laitch]

Thank you for the reply and I have done all things mentioned.

What other things have you done that you haven't mentioned?

[rbm]

As you see in the diagram Laitch posted, you should measure +12V on the LSR Green wire when the ignition is in the ON position.  The kill switch and its downstream circuitry is parallel to the LSR and its downstream circuitry, so the position of the kill switch is irrelevant to the LSR measurements.  You should also measure +12V on the LSR's Red wire at all times, irrespective of the position of the ignition or kill switch.


When you turn the ignition ON, the LSR should pick.  The LSR will apply +12V to the Green/Blue wire when it picks and this will power the downstream circuitry (Headlamp, Horn, Temp Sense Relay, Alarm, Flasher).  When you press the start button, the LSR should drop and remove +12V on the Green/Blue as long as the starter motor is running.  Once you release the start button, the LSR should pick again and 12V reappears on the Green/Blue.


Power to operate the rear running light comes through the BMU.  That power comes from the aforementioned kill switch circuit through fuse 1.  There is power coming from fuse 2 to the BMU. If your concern is the lack of a rear running light, you should concentrate on the BMU.

[Kckershovel]

Okay I have 12v on red wire but it doesn’t send 12v to the green and blue wires. I also have 12v the opposite side of the red wire I’m not sure the color but it’s not black or red or green and blue so the other one. I have no power to the green and blue wires. That is what I need.

[rbm]

Relays have standard pin designations
85 and 86 are coil connections
30 is the common contact connection
87 is the normally open contact connection
87A is the normally closed contact connection

LSR coil: one side (86) is connected to Green, the other side (85) is connected to Black
LSR contacts:  common contact (30) is connected to Green/Blue, N.O. contact (87) is connected to Red
The LSR does not have an 87A contact.

Which other wire are you talking about???

You should measure 0V on Green/Blue with ignition off, and at 12V with ignition on.  If not, the N.O. contacts in the relay are defective or the contacts int he socket are defective (not making contact with the relay's terminal blades).
 

[Laitch]

[The Mighty Gryphon]

I hate to add another cook stirring the soup, but a couple questions come to mind as I try to follow the discussion.  There are only three components in the starter load shed circuit, the start relay, load shed relay, and the starter.

If I was troubleshooting this problem, the first thing I would want to work is the Start Relay.  Three tests here:

1. Turn ignition on and press start button.  Do you get 12v from button to the terminal on the start relay?  No, you have a button or wiring problem.

2. Does the Start Relay activate with 12v applied to the coil?  No, there is a problem in the coil or the internal mechanicals of the relay.  Open the relay and check for anything hanging up the contacts.  Check the coil resistance.  Is the coil an open circuit with infinite resistance?

3. If the coil energizes and closes the contacts, does the output of the relay go to 12v?  Does the 12v show up on the starter?  No, you have bad contacts or wiring. 

The Load Shed Relay should be energized when the ignition is turned on.  This is what makes the headlight, etc. come on when the key is turned on.  The relay needs to be grounded through the starter motor.  A couple tests will tell what the problem is with the relay.

1. Does the Load Shed Relay get 12v to the coil when the key is turned on?  No, there is a problem in the key switch or the wiring.  The key switches are notorious for going bad and needing cleaning after all these years.

2. When the terminal on the starter motor is grounded with a jumper wire when the key is on does the Load Shed Relay activate?  No, there is a problem somewhere in the commutator or brushes in the starter motor. 

3. What is the resistance to ground from that terminal on the starter motor?  It should be almost zero, just a couple ohms.  If not, remove the starter motor and clean the commutator and check the brushes.  A bad ground here will not allow the Load Shed Relay to activate and prevent the motor from developing full torque.

4. Is the Load Shed Relay of the proper type?  The contacts should be normally open with infinite resistance betwen them when the relay is not energized.  If the resistance is zero or very low, you may have the wrong relay.  Yes, it has happened.  Don't ask me how I know.  Open the case and check.  Activate with 12v and watch what happens. 

I am pretty sure that if you go step by step and correct any of the problems before going to the next step, you will find the problem.

[Kckershovel]

first I have new to me used ebay starter solenoid on its way.


1 yes I have power from start button to terminal on relay. I get 12v to the starter solenoid but I do not get power to the starter. That’s why I have solenoid on its way.


Lsr


1 I have 12v at load shed relay.


2 Nothing happens when I ground the starter terminal. It’s my understanding if it were a starter problem my lights should change me on when performing this test. They do not.


3 I will check resistance tomorrow.


4 I don’t know if lsr is proper type. I swapped it for the horn relay and still no lights.


At the load shed relay I have 12v at both 86 and 87 with the relay pulled out testing with meter... Is that normal?


Lights work only if lsr is pulled and jumper is run from red power to green and blue wires at the lsr plug.

[The Mighty Gryphon]

Don't skip steps, you need the previous step working to do the next.

When you say you have 12v at the LSR, is it on the coil terminal?  If so, grounding the starter terminal should activate the LSR and turn on the lights.  If not, the relay or wiring from the relay coil to the starter terminal is bad.

Have you opened the cases on the relays to see what condition the internals are in?

[The Mighty Gryphon]

What is the resistance between terminal 85 on the LSR socket and the terminal on the starter?   It should be very close to zero.  If it is infinite, there is a bad connection or wire between them. 

With 12v on terminals 86 and 87 the relay should activate and turn on the lights when the starter is not running.   Your problem is either a bad relay(you say you swapped in another) or a problem in the wiring from terminal 85 to the starter. 

[The Mighty Gryphon]

Haveyou measured the resistance across the coil terminals on the starter relay? 

One coil terminal on the starter relay gets 12v from the start button.  When the button is pushed, what is the voltage on the other terminal?  What happens when the other terminal is grounded with a jumper to the frame?

[The Mighty Gryphon]

There are two main ground points on your bike with a bunch of brown wires connected to them.  One is on the top tube of the frame under the tank, and the other is on the left side of the intermediate section between the engine and transmission just above the shifter. 

Look closely at both places for any brown or black wires that may not be connected. 

[Kckershovel]

So a brake from the load shed relay for a moment....


    I receive my new to me starter relay put it on and still nothing. I checked that I have 12v to the black and yellow wired when start button is pressed. I noticed I have roughly 2v to the brown and red wire. This seemed odd to me and got me wondering where the starter relay gets its ground from. I assumed it should be the brown and red wire. So I took my old relay and applied 12v to black and yellow and ground to brown and red wire and what do you know the relay clicks like it should.


So my question is this. Why would I show 2v to brown and red wire going to starter relay with bike not running? It would seem I need this to be grounded for the start button to work....

[Inge K.]

The starter relay coil is grounded through the ignition ECU, not a unusual problem that this connection is lost.
This setup is to avoid the starter to run if you push the starter button while the engine is running.

[Kckershovel]

So is the fix to cut the red and brown wire to the starter relay and ground to frame or how do you fix that ground connection through the ecu?

[Inge K.]

1. You can ground the brown/red wire.... but the safety function ....while engine is running, is gone.
2. You can find a second hand ignition ECU.

[Kckershovel]

Would that have anything to do with why my load shed relay is cutting power to fuse 7 like the start buttons is being pressed even when it’s not or is that an unrelated issue?


I have no background on this bike just trying to bring it back from the dead.

[Inge K.]

Would that have anything to do with why my load shed relay is cutting power to fuse 7

No.
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Is the LSR the genuine one from BMW, or is it just a generic one?
If it's the genuine one it should have the part number on the top of the housing.