12 volts is 12 volts.....right?

Discussion in 'Electrical' started by cacasal, Apr 9, 2010.

  1. cacasal

    cacasal Member

    6
    0
    0
    I hooked up a voltmeter to the positive ( Center lug on a Spyke coil ) and to the starter ground. It was a "LED" unit that goes through it's self testing cycle when you turn on the ignition. It read correctly as soon as I turned on the key. Immediately, upon start up, it started to cycle through it's self test procedure over and over. I shut it off, checked all my connections ( including ground ) and every thing was OK. I called the vendor. "You can't hook that up to the coil" he says. HUH??? isn't 12 volts 12 volts anywhere?
    There is no computer on this carburated motorcycle, which I don't think would alter that anyway.
    The problem was resolved, and to humor "them" I'll hook it up elsewhere, but I don't understand the reasoning behind his statement. Can someone enlighten me please?
     
  2. Hoople

    Hoople Account Removed

    7,198
    0
    34
    Answer can be yes or no. Not enough info to answer your question. Is there a separate trigger unit to trigger the coil or is this entire unit self contained. If you are placing your voltmeter on the primary of the coil, the answer is no. If your placing your voltmeter to the B+ supply of a self container module, answer is yes. Need to see a schematic or basic wiring diagram of your unit to tell you a positive answer and reason why.
     
  3. Thorns

    Thorns Active Member

    205
    26
    0
    Well you can have 12 volts in a wire, but there are other factors.

    Thorns
     
  4. cacasal

    cacasal Member

    6
    0
    0
    Imagine a wire from the battery to a key switch...when you turn on the key the wire from the key switch goes to the coil (B+) To that terminal, there is also a wire from the Spyke single fire ign...which also has wires to: 1) the front cyl. coil lug..2) the rear cyl coil lug...3)my tach....and 4) the vos.The unit is all self contained and is located in the nose cone.
    I have run a regular volt meter ..2" round gauge ( analog ) with no adverse effects, hooked up to the same location.
    Thanks,
    Carlos
     
  5. Hoople

    Hoople Account Removed

    7,198
    0
    34
    Carlos, I see no problem with what you are doing. As long as that "supply" wire that is coming from the ignition switch is beefy enough to support the total current load, your fine. Without doing the math, I would say 16 gauge is all you need and 14 gauge would be MORE than you need. And if it's 12 gauge,, you could keep stacking on more wires!!:p:p

    I think the vendor just did not fully understand what you were saying.
     
  6. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

    8,176
    98
    16
    I am a bit confused as far as what are you hooking up: you have your ignition coil, there are 3 connections, on on one you have B+ (12V), and 2 other connections, there is an LED device of some sort that is going thru self test over and over and you have a tach connection...

    What are you trying to hookup and get working, and what is this LED device that goes into self test mode and stays there? A picture would speak volumes...
     
  7. cacasal

    cacasal Member

    6
    0
    0
    NEWHD74FAN....The following is part of my original post: "I hooked up a voltmeter to the positive ( Center lug on a Spyke coil ) and to the starter ground. It was a "LED" unit that goes through it's self testing cycle when you turn on the ignition. It read correctly as soon as I turned on the key. Immediately, upon start up, it started to cycle through it's self test procedure over and over"
    I could post a picture of a volt meter...but I think we all know what one looks like. This voltmeter is an led unit that has several lights that indicate the state of charge. When you fire the bike up, it indicates how much it is charging. Example 10 volts= 1 red light, 11 volts= 2 red lights, 12 volts 1 amber light, 12.5 volts 1 green light,....and so on, up to 15 volts or so. The last two lights are red. It's power consumption is NIL since they are LED's . So it hooks up just like any voltage meter. One lead to positive (* in my case, I chose the same lug on the coil to which the power from the ignition switch goes ) and the other wire to ground ( I chose to go to the same ground as the starter)
    I hope this is now clear enough. Thank you.
     
  8. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

    8,176
    98
    16
    I was thinking "new fangled" LCD/LED DMM units that had no self test mode...they just flashed if overrange OL or 1.999 ....sorry.

    The LED charging system diagnostic tool you describe probably is set up with limited range for monitoring charge voltage using color coding, and seeing an overvoltage is causing the display you are thinking is a self test mode to constantly reset and protect itself. It also may be setup for reading DC direct current and not AC alternating current which it is not made to see either, indicating a "bad" charging system.

    May I suggest you go to Harbor Freight w/ 20% coupon and pick up a modern DMM normally costing $10 to $50 for a bargain price of a $1.99, it will give you an "honest" reading and allow you to scale up to read that odd voltage...you are correct in your acessment with that "tool" 12V is not 12V when all it is set up to read is 10 to 15V.
     
    Last edited: Apr 10, 2010
  9. cacasal

    cacasal Member

    6
    0
    0
    NEWHD74FAN...."May I suggest you go to Harbor Freight w/ 20% coupon and pick up a modern DMM normally costing $10 to $50 for a bargain price of a $1.99, it will give you an "honest" reading and allow you to scale up to read that odd voltage...you are correct in your acessment with that "tool" 12V is not 12V."
    I have one of those gizmos you discribe. Had one in my saddle bags for over 20 years...super cool. The one I'm using is made for motorcycles by a large aftermarket manufacturer( importer ) They are small...about 2" X 1 3/4 "X 5/16ths, and can be put easily anywhere. ........ So, I think that the answer in this case, is: 12 Volt at the B+ lug on my coil is 12 VOLTS ( or whatever the battery voltage is at the time )
    `
     
  10. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

    8,176
    98
    16
    Yes, as I have said before, using test equipment is like a doctor trying to make a diagnosis by feel and a stethocope...you will get a reading that you expect, but still make a wrong diagnosis.