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Thread: Installed battery, now horn blaring and all electrical accessories are on!

  1. #1
    Registered Member

    2010 Mazda 5

    Join Date
    Nov 2011
    Location
    Ottawa, Ontario
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    6

    Installed battery, now horn blaring and all electrical accessories are on!

    I installed a new battery and when I connect the second (negative) battery cable the horn blares constantly and all electrical accessories are on i.e. parking lights, windshield wipers, interior fan etc. and keys and remote fobs have no effect; cannot turn off accessories/horn, cannot lock/unlock or start car. I've pulled the horn fuse (to work in quiet :-) but cannot attach the negative battery cable without all the electrical things turning on.
    Advice/recommendations wanted on why "electricity is flowing" when I attach the second battery cable and how to stop it and get control of the ignition/locks again with the keys/remotes.

  2. #2
    Registered Member

    2012 Mazda 5

    Join Date
    Apr 2013
    Location
    Vancouver
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    679
    Fried BCM?

  3. #3
    Registered Member

    2010 Mazda 5

    Join Date
    Nov 2011
    Location
    Ottawa, Ontario
    Posts
    6
    Battery was installed backwards.
    Now all electrical items work and fobs synced.
    Only problem is no sound at all when I try to start the engine. Possibly starter relay was damaged when battery connection was reversed??
    Or is it simply something more I have to do with the anti-theft system for it to recognize the key?

  4. #4
    Registered Member Silentnoise713's Avatar

    2008 Mazda5 Grand Touring; 2009 Honda Fit Sport/Nav MT

    Join Date
    May 2010
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    PA
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    2,571
    Check the fusible link (near battery). Google it for the Mazda3 for more info. If it is blown, technically you are suppose to replace the whole harness or you can splice in your own fuse -your money/choice.
    Stuff for sale:
    YellowSpeed DPS Coilovers - cheap



    ^http://www.wingood.com/flagselect.asp

    My Thread
    ^http://www.mazdas247.com/forum/showt...oise713-Thread

  5. #5
    Registered Member

    2010 Mazda 5

    Join Date
    Nov 2011
    Location
    Ottawa, Ontario
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    6
    I've got my car back now and it's running fine. The cause of the problem: I installed the new battery backwards (i.e. positive cable to negative post, negative cable to positive post. After re-installing the battery the correct way:
    - I replaced the blown 15A fuse for the interior overhead lights;
    - Confirmed that all electrical accessories worked;
    - Re-programmed the keys and remotes so they communicated with the car's computer;
    - Attempted to start the car. All instrument panel lights indicated that the anti-theft system was accepting the keys;
    - There was no sound from the starter solenoid/relay therefore no engine cranking - no start.
    - Towed the car to the dealer.

    What the dealer did:
    - Determined that the main fuse inline with the positive cable had blown; Installed a new main fuse; started the engine; determined that the power steering was not working; mechanic tried but was not able to configure (program) and activate the power steering electronic control module; price of a new power steering control module and motor unit: $1,400 (!); I suggested looking for a used one; they found one for $500. The mechanic decided to swap the used control module and install it on my (original) power steering pump. I was charged 2½ hours labor plus the price of the parts.
    I was fortunate that none of the other control modules (i.e. electronic modules) were damaged.

  6. #6
    Booga Booga? phunky.buddha's Avatar

    2009 Mazda5 Sport

    Join Date
    Jul 2011
    Location
    DFW Metro, TX
    Posts
    1,560
    Ouch. Backwards battery could end up blowing up quite a bit of stuff- glad your car is working again!

  7. #7
    Registered Member

    mazda 6

    Join Date
    Jan 2019
    Location
    ny
    Posts
    1
    Ran into this issue after installing a new battery backwards (never install a battery in the middle of the night without light lol). Push start did not work, along with advanced key fob, power windows, power locks, lights, radio, bose, etc..

    I blew out the main fuse (and a couple others) but the ECU/PCM was safe. This happened in a 2009 Mazda6, but I'd bet the electricals are similar. Also, the alternator probably received some kind of damage/wear because it's not protected by the 125A Main Fuse.

    Edit: All dashboard lights were on and headlights worked.
    Last edited by john2496; 01-29-2019 at 02:20 AM.

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