Disconneted wiring harness by HVAC blower motor?
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This is a discussion on Disconneted wiring harness by HVAC blower motor? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Does anyone know why this harness came from the factory disconnected? It's down by the blower motor and just hangs ...

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    Registered User UAC-2145's Avatar
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    Disconneted wiring harness by HVAC blower motor?

    Does anyone know why this harness came from the factory disconnected? It's down by the blower motor and just hangs out there. I was curious so I connected it and turned the key on. I heard a relay clicking on and off and the cooling fans would turn on and off. They are unplugged now. I have no clue? I'm thinking its some kind of by-pass circuit and has a troubleshooting/diagnostic function.

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    \_(ツ)_/ Rambo's Avatar
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    What car do you have?
    I know on Legacys, the green ECU test mode connectors are there (green Molex-type connectors with a single wire in each connector), but on all Imprezas and Foresters, the test mode connectors are under the steering column.

    When connected, the radiator fans will start cycling, you'll hear the fuel pump cycle, and the CEL will start flashing. This mode is needed for flashing ROMs to the ECU, but should be disconnected all other times.
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    Registered User UAC-2145's Avatar
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    Thanks for the reply. I have a 2013 Impreza WRX. Yes they are the green Molex-type connectors I assume I didn't do any harm to the ECU?
    2013 Plasma Blue Pearl Impreza WRX Sedan

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    Quote Originally Posted by UAC-2145 View Post
    Thanks for the reply. I have a 2013 Impreza WRX. Yes they are the green Molex-type connectors I assume I didn't do any harm to the ECU?
    If I understand the service manual correctly, your "test mode" connectors are used by dealers to check some fans and relays when a new vehicle is delivered to them.

    On older WRXes, the "test mode" pair had to be connected to flash the ECU. (The connectors were right next to the OBD-II port, beneath the steering column.) They had to be disconnected to run the car. 2008 and newer WRXes don't need that.

    Short version: you didn't damage anything. I don't think that "test mode" applies to your ECU.

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