Cigarette adapter voltage question

Discussion in 'Dakar champion (950/990)' started by gmanny, Nov 23, 2019.

  1. gmanny

    gmanny n00b

    Joined:
    Nov 23, 2019
    Oddometer:
    2
    Location:
    Tacoma, WA. USA
    I'm troubleshooting an issue with some auxiliary lights and found that when the bike is off, the cigarette lighter on the dash reads above 12v. When I turn the key, the voltage drops to below 2v, and stays there even after starting the bike. Turn the bike off and the voltage returns to ~12v. Same behavior on a circuit I ran to the battery for my aux lights. Is this a problem with the RR? Any other ideas?
    #1
  2. gearheadE30

    gearheadE30 @LC8Adventures Supporter

    Joined:
    Jan 20, 2012
    Oddometer:
    2,137
    Location:
    Indiana
    950 or 990? Where is the dash cigarette lighter tied into bike power?

    This isn't entirely unusual if you are tied into one of the ACC connections behind the dash. The wires are tiny, the connectors tend to get dirt in them which increases resistance, and everything goes through the keyswitch which is also known for getting dirty. Some of these things are more or less common depending on if you have a 950 or a 990. Later 950s also have the carb heaters tied into the ACC port, which draw a fair amount of current through those tiny wires and switch contacts. That all means more voltage drop. Check the voltage at the battery terminals with a good multimeter and see if you get different results; that's probably the best way to check.

    If everything checks out the same and even the battery has low voltage with the engine running, check that the battery and regulator connections are clean, and that your main relay is good. I've seen some issues with the connection between the battery terminal and the 30A main fuse for the rest of the bike cause some problems here if things start getting corroded.

    I don't think your RR is starting to fail. The bike won't run if it's actually at 2V. The fuel pump on a 950 will stop working around 9 volts, and the 990 will stop working around 10 in my experience.
    #2
  3. 1coolbanana

    1coolbanana Long timer

    Joined:
    Aug 25, 2009
    Oddometer:
    5,734
    Location:
    NW Sydney, Australia
    Fully charged battery should read about 12.7 - 13.0 volts
    While running, voltage should be 14.2 - 14.4 volts.
    Check the voltages elsewhere and not at the cigarette lighter, like at the starter relay to isolate the issue.
    The cigarette lighter is good for 10 amps but maybe not if old, corroded etc.
    #3
  4. gmanny

    gmanny n00b

    Joined:
    Nov 23, 2019
    Oddometer:
    2
    Location:
    Tacoma, WA. USA
    Thanks to you both, appreciate the help.

    The bike is a 2008 990 Adventure S. The cigarette adapter is connected via the ACC wires. As advised, I will check the voltage at the starter relay to see if I can isolate this. Thanks again.
    #4