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Thread: 2004 honda civic-- no airflow

  1. #1
    Join Date
    May 2011

    Question 2004 honda civic-- no airflow


    How can I tell if the blower motor needs replacement or the transistor or the control knob assembly. Nothing happens when I turn the blower control knob for the fan. No airflow at all. If I turn on the a/c, the compressor starts for a split second and then turns off. There were no symptons before this happened, everything worked fine the day before.


  2. #2
    Join Date
    Jan 2007


    Hi billvalenta,

    Take a a look at the wiring diagrams in the manual for your car (in the copy I'm looking at, they're on pages 12-24 and 12-25). Since this all happened at once you need to concentrate on the components that could affect both the blower motor and the compressor clutch. We can't diagnose problems from a remote location, but the first thing that jumps out at me is that the PCM and a multiplex control unit figure into the circuit that controls the compressor clutch, which in turn feeds power to the blower motor relay. So, study those diagrams and perhaps by process of elimination you can pin-down the problem. Unfortunately, some of the components can't be tested by "normal" methods.

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