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Thread: Electrical gremlin ???????

  1. #1
    Registered User jgr451's Avatar
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    Electrical gremlin ???????

    1995 R100RT.Went for a ride ,all was well, except that the rear park/license plate light was not working. Opened up,changed bulb, still not working. The front park light does not work either for no evident(to me at least!)reason.

    Looked at it again today and the fuse on that circuit is blown and blows with every attempt to switch on the ignition.No ignition lights, horn, lights. Disconnected that plug from the rear that carries the rear park light, brake light and turn signals. Fuse does not blow, but no ignition light display etc.

    While fiddling and before I discovered the fuse was blown,I heard an odd noise from underneath the gas tank,as though compression were escaping and for some reason I thought the starter relay had blown? No smoke ,no smell, no visibly damaged wires.

    Last thing I did before I finished fiddling last week was applied front and rear brakes to ensure the brake light was working. Engine off, switch on.It was.

    The battery is showing 12 v,so it has not been drained by an open circuit.

    Any testing or troubleshooting suggestions?
    Thanks in advance.
    Sometimes,nothing is a real cool hand.

  2. #2
    Administrator 20774's Avatar
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    You might try putting a 12v bulb across the fuse contacts so you can continue trouble shooting without having to replace fuses all the time.

    The noise under the tank...your bike probably has the solenoids that shutoff fuel. That might be what you were hearing. You might pull the tank and look at the wiring in that area...see if you can find a frayed wire, especially if it has the coloring of the power wire to the tail light.
    Kurt -- Forum Administrator ---> 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!

  3. #3
    MOA #24991 Pauls1150's Avatar
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    Fuses typically blow because of a short, not an open. You probably have a chafed wire, or possibly some conductive debris inside a socket or harness connector.
    You've uncovered several major clues that point where you should look.
    From your description, look at the gray wires with a black runner in the schematic. Specifically look at the ones to the "right" ("downstream") side of the fuse. (You should be able to save this schematic to your PC and then use the "View/Zoom" to magnify it.)
    Attached Images Attached Images

  4. #4
    James.A
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    I totally agree with Kurt on using a test light on the fuse contacts. The way to chase this type of thing is to identify, by wire color code, which devices are in line with the fuse. (wiring diagram needed) Then eliminate (dis-connect) them 1 by 1 until the test light does not glow when the key is turned on. When the test light does not illuminate on the key turn, you have found which component creates the draw that is popping fuses.

    Example: I recently lost my tail lights and turn signals on my /7 with sidecar. Opened the headlight to reveal the fuses. Found the wire colors on that fuse. I then pulled the spade connectors associated with that fuse until the test light glow did not return when switching on the key. It was a green and black wire which I then traced to the rear brake light switch. I had pinched it with a large nut when installing the sidecar sub-frame and it took about a month for the insulation to become breached, creating a short.

  5. #5
    Registered User jgr451's Avatar
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    Thanks for the suggestions.I was pondering having to buy 15 or 20 fuses to get through the testing process!!They're not that pricey but it seems wasteful.I have a few ideas about where else to look,thanks to all who replied.
    Sometimes,nothing is a real cool hand.

  6. #6
    Registered User toooldtocare's Avatar
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    I discovered a short in the lighting circuit to my voltmeter on my 95 RT. The wire broke off and was touching something under the "dash." It took me forever to find it because the fuse only blew once in awhile. Do not forget to look there too. If my memory serves me right, when it blew it also took out the tail light.

  7. #7
    Alps Adventurer GlobalRider's Avatar
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    Quote Originally Posted by jgr451 View Post
    Disconnected that plug from the rear that carries the rear park light, brake light and turn signals. Fuse does not blow, but no ignition light display etc.
    So the short is in that section of wiring. Disconnect that plug and perform the following test. Ignition off as no power is required.

    I am unaware of the construction of that harness in that do they just source power to loads (park, brake lights, etc) or does that harness also have a ground return line?

    If the wires in that harness just source power to the loads, connect a DMM in the 200 ohms continuity beep mode; connect one probe to a good ground and the other probe to the pins in the connector till it beeps. If it doesn't beep, move the harness about till it does. It'll confirm your short and maybe give you an idea where to zero in.

    If a ground wire is within the harness, just connect the probe to that pin.

    Use a straightened paper clip to insert into the connector if needed.

  8. #8
    Alps Adventurer GlobalRider's Avatar
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    By the way, this is how short circuits start.

    This harness was chaffing against the underside of my R1150 GS Adventure gas tank due to incorrect routing by the factory.

    Luckily, I caught it in time and rerouted the harness. Its also why it is a good idea to remove things such as gas tanks periodically to inspect things.


  9. #9
    Registered User lmo1131's Avatar
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    Brown AND Red.... that would have been an interesting story.
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  10. #10
    MOA #24991 Pauls1150's Avatar
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    Like we used to say at work: "Tune for maximum smoke."

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