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Thread: Electrical issues with MK 5 2.0 FSI BLX engine

  1. #1
    Join Date
    Sep 2021
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    Electrical issues with MK 5 2.0 FSI BLX engine

    The problem is an intermittent one and seems to connected to cold ambient temperature, I go to start the car and the dash is dim, (I recently replaced the battery (<3mth) AGM 760 CCA), when I turn the key - nothing dash goes out - no lights on dash, I use my jump pack to start no problem. when I get to my destination switch off engine and stereo stays powered as does the dash. Come back to the car and it's dead again, start car with jump pack and off I go. Switch car off for the day all ok, next morning no problems. When I want to go home after work it's dead again - start car with jump pack and drive home switch it off and it's instantly dead - wait 20 seconds and power is back - but then wont switch off power to stereo or dash. Do these have a battery control module or relay that could be faulty - if so where is it?

  2. #2
    Join Date
    Jul 2007
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    Brissy
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    This really sounds like some poor connections.
    Check the battery terminal connections are tight and free of corrosion.
    Engine fuse box is next to the battery. I would check the fuses in that area, at the front of the engine fuse box there are a lot of wires held in with bolts and high rated fuses. Check these are all tight, 10mm bolts I think.

    There is a main relay in the engine fuse box. It controls the power to the engine components, but not the starter. I had intermittent issues starting, crank but no start. VCDS scan showed this up for me and I replaced, no issues since.

    Next would be an output test of the alternator, check there is close to 14v at the battery when the engine is running.

    If all of those tests pass, get a proper diagnostics scan.
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  3. #3
    Join Date
    Sep 2021
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    Electrical issues with MK 5 2.0 FSI BLX engine

    Quote Originally Posted by JustCruisn View Post
    This really sounds like some poor connections.
    Check the battery terminal connections are tight and free of corrosion.
    Engine fuse box is next to the battery. I would check the fuses in that area, at the front of the engine fuse box there are a lot of wires held in with bolts and high rated fuses. Check these are all tight, 10mm bolts I think.

    There is a main relay in the engine fuse box. It controls the power to the engine components, but not the starter. I had intermittent issues starting, crank but no start. VCDS scan showed this up for me and I replaced, no issues since.

    Next would be an output test of the alternator, check there is close to 14v at the battery when the engine is running.

    If all of those tests pass, get a proper diagnostics scan.
    I have VCDS and scan showed nothing but then this is an intermittent problem and the car wasn't playing up at the time but also no stored codes, I have ordered an ignition switch just to take that out of the equation.

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