Blower motor wiring connector melt in vehicles

Discussion in 'The Projects Forum' started by vijayendhiran.p, Feb 26, 2016.

  1. vijayendhiran.p

    Thread Starter New Member

    Feb 26, 2016
    1
    0
    I am seeing in some of the cars blower motor connector is getting melt. Which is the continuous load in the vehicle. voltage is 12.8 Direct Current.
    Current will be 23.8 A steady state.What are all the potential cause. 4 Sq. mm cable is used
     
  2. JohnInTX

    Moderator

    Jun 26, 2012
    2,345
    1,028
    That looks like it is caused by loose or poorly crimped connections. It is also possible that the connector tabs are not the right thickness for the connector contacts. The high current causes heating due to resistance caused by the loose connection. As the connection gets hotter, the resistance gets higher which makes things worse. The solution is tight connections with quality materials.
     
  3. tranzz4md

    Member

    Apr 10, 2015
    139
    28
    John in Texas has it right on. This is an extremely common failure mode for any loose electrical power connection. Heat cycling exacerbates the problem, and can initially trigger the problem, and the heater blower motor in a car experiences heat cycling like few other common loads. Spring retention of power carrying conductors is a very, very troublesome practice, because the electrical resistance heating will increase to the point where the temper of the metal (working as a spring to establish and maintain electrical contact within the joint) will be lost and the connection will become intermittant and high impedance, leading to catastrophic failure of the joint, as well as electrical insulation failure due to its overheating and burning away.

    The mechanical connection needs to be moved to a location with fewer and smaller heat cycles, and/or substantially upsized/oversized.
     
    Last edited: Feb 27, 2016
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,031
    3,803
    If it is always the same brand of vehicle (or same brand of blower - look for moles-in manufacturer logo), you should report the failure to your national transportation authority. Most countries would force a recall of the vehicle for a repair paid for by the manufacturer.
     
  5. #12

    Expert

    Nov 30, 2010
    16,283
    6,795
    These failures are so common on alternators that the rebuild kits are in blister packs hanging in the aisles.
     
    GopherT likes this.
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