Author Topic: K100 tail light/parking not on w/ ignition on  (Read 8665 times)

Offline Marietta

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K100 tail light/parking not on w/ ignition on
« on: August 26, 2017, 07:34:53 PM »
I'm in need of help..... Tail light/parking light work in middle position of ignition but not when switched to third position (ignition on). Head light, dash lights, etc. all working in third position..... Checked continuity of my ignition switch against another switch from working bike and results were the same.... Checked voltage at bulb monitor relay w/ ignition switch at middle position, grey wire(parking/tail light) at 12 volts.... W/ ignition switch at third position (ignition on) there is no result at grey wire but do get 12 volts at green wire (headlight)..... Is this normal?....at what point does power go to the parking/tail light circuit?........ Does this tell me my relay is bad or am I not deep enough in to get good test results.....Hoping for a simple explanation as you can tell I have a simple mind for this sort of thing...... Maybe left handlebar switch?
   David
  • Central Ohio
  • 1987 K100RS

Offline rbm

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Re: K100 tail light/parking not on w/ ignition on
« Reply #1 on: August 26, 2017, 08:18:29 PM »
Dirty ignition switch.  You'll need to disassemble and clean it.


When in P-position, Red is connected to Grey, which is why you see +12V on BMU Grey in that position.  When in the R-position, Grey gets power from Grey/Blue.  This contact pair in your ignition switch is failing.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline Laitch

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Re: K100 tail light/parking not on w/ ignition on
« Reply #2 on: August 26, 2017, 10:52:15 PM »
Hoping for a simple explanation as you can tell I have a simple mind for this sort of thing......
Success will be elusive for a simpleminded mechanic, David. :giggles Look at yourself differently and look at this tutorial, also.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline The Mighty Gryphon

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Re: K100 tail light/parking not on w/ ignition on
« Reply #3 on: August 27, 2017, 09:31:38 AM »
Dirty ignition switch.  You'll need to disassemble and clean it.


When in P-position, Red is connected to Grey, which is why you see +12V on BMU Grey in that position.  When in the R-position, Grey gets power from Grey/Blue.  This contact pair in your ignition switch is failing.


+1.  Have had problems with that switch on 2 of three bikes.  The design is bad in that it doesn't have enough pressure to make contact through the slightest amount of dirt or corrosion. 

One of my switches looked clean inside and still wouldn't give a reliable connection.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline Marietta

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Re: K100 tail light/parking not on w/ ignition on
« Reply #4 on: August 27, 2017, 01:36:38 PM »
Thanks for all the replays...... Yes I saw Don Eilenbergers tech...... Got as far as removing the set screw....two screw drivers and a lot of PB blaster later, took the pig-tail to a guy with a good working unit.... Did comparative continuity tests and both seemed the same (per prior post)....... He had previously had issues w/ set screw and explained his procedure to grind away housing around the screw until able to grab and turn w/ vice grips....... Was hoping not to need to go that route just yet...... Hints?
Next question.... In wiring diagram, does ON position indicate that gr/bl is getting power from rt?...or is gr/bl power derived from another source? or gr/bl is hard connected to rt not switched?
  • Central Ohio
  • 1987 K100RS

Offline rbm

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Re: K100 tail light/parking not on w/ ignition on
« Reply #5 on: August 27, 2017, 02:47:28 PM »
Quote
n wiring diagram, does ON position indicate that gr/bl is getting power from rt?...or is gr/bl power derived from another source? or gr/bl is hard connected to rt not switched?
In the Park position, Grey gets power from Red (i.e. unswitched +12V). This provides power to parking light circuit. 


In the On position, Red instead provides power to Green,which subsequently provides power to the load shed relay (LSR).  Grey gets switched 12V power from Grey/Blue, which itself gets power from Fuse #7 via the LSR and right hand light switch.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline Marietta

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Re: K100 tail light/parking not on w/ ignition on
« Reply #6 on: August 27, 2017, 04:57:33 PM »
Thanks Robert......... Appreciate the clarification


Again thanks to all who replied.


David
  • Central Ohio
  • 1987 K100RS

Offline Marietta

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Re: K100 tail light/parking not on w/ ignition on
« Reply #7 on: September 03, 2017, 07:12:31 PM »
Well the cleaning of the ignition switch per Laitch/Eilenberger was a success..... Got past the sticky set screw... Not very dirty but I carefully cleaned and reassembled......
But I still have my problem of tail light/parking light not working in the on position... My ignition wiring looks good with good connections...... Any other thoughts?...... Load shed relay?.... :dunno
Another ignition switch is available to me but at a cost $$$$.....


David
  • Central Ohio
  • 1987 K100RS

Offline rbm

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Re: K100 tail light/parking not on w/ ignition on
« Reply #8 on: September 03, 2017, 08:21:36 PM »
Try some more testing until you find out the failing component.  Substituting parts of the bike randomly is the most expensive debugging technique available to you.

So, with any electrical problem, work backwards from the failing component until you've found the problem.  Use the schematic and reason out how the circuit works so that you know what to expect when you test.

1. Have you checked that your cleaning has been successful?  You expect power at Grey/Blue gets transferred to Grey when in the second position.  So, is there power on Grey/Blue to begin with?

If the answer is "yes there is", and nothing is on Grey, your cleaning has been unsuccessful.

If the answer is "No there is not", then the problem is further up stream.  Do you have a headlight switch on the righthand switch cluster?  Is there power on the Grey/Blue PIN 7 wire from that switch (check under the tank)?

If the answer is "yes there is", then there is a wiring failure.

If the answer is "No there is not", then the problem is further up stream.  Do you have power on Green/Blue PIN 3 wire?  Maybe a problem with the righthand switch cluster.  Maybe a problem with Fuse 7 or the LSR.

Do some testing and post your results and we'll try to work through this.  I would not suggest replacing components just yet.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline Martin

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Re: K100 tail light/parking not on w/ ignition on
« Reply #9 on: September 04, 2017, 12:16:27 AM »
Might seem obvious but check the globe.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Marietta

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Re: K100 tail light/parking not on w/ ignition on
« Reply #10 on: September 04, 2017, 07:03:44 PM »
Might seem obvious but check the globe.
Regards Martin.
Tail light works in park position......... :bmwsmile but now..... Tail light also works in on position.
Following Roberts advice....determined that wiring was a likely source of the problem.... Tracing gr/bl wire found a connection under the tank had become dislodged in connector w/ multiple wires..?!?... Reconnected and good to go..... :riding:
Result of event.......now have a clean ignition switch (just slightly dirty before), better understanding of wiring system and knowledge that several different wiring diagrams are necessary to diagnose my bike.
Thanks for the help.
David
  • Central Ohio
  • 1987 K100RS

Offline Marietta

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Re: K100 tail light/parking not on w/ ignition on
« Reply #11 on: September 04, 2017, 07:12:11 PM »
A clarification of my first post..... I said that my instrument lights worked in the on position.....but really, only the idiot lights were on...... After checking in the dark did I see that illumination lights which are powered the gr/bl wire were in fact not working...... But as stated, all is well now.
David
  • Central Ohio
  • 1987 K100RS

Offline rbm

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Re: K100 tail light/parking not on w/ ignition on
« Reply #12 on: September 04, 2017, 09:36:23 PM »
Good to hear its working now.  Much cheaper fix than a new switch.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

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