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  • Inside a central locking pump

    I was curious to see inside one of these - thinking maybe it had some moisture ingress or bad contacts. Opening it is the only way to isolate the pump inside it for testing.

    There are a good number of plastic clips that secure the base as cover to the unit. Tease those up gently all around and the cover lifts away quite easily.

    Look out for location of a couple of foam pads that help keep the circuit board snug.
    Attached Files
    Paul Nugent
    Webmaster http://S2central.net
    Administrator http://S2forum.com

    1994 S2 Coupe ABY - aka Project Lazarus
    2001 A6 allroad 2.5TDi - family tank
    2003 S4 Avant 4.2 V8 - daily burble

    Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

    There are only 10 kinds of people that understand binary - those that do, and those that don't

  • #2
    Carefully you can then lift out the PCB - taking care of the long neck on the control valve. The blue and red wires connect from the PCB to the actual pump itself.

    The pump is mounted on four rubber bungs - the assembly lifts out easy enough and you'll see how the pump is connected to the control valve by means of the air pipe - as a funky pneumatic closed loop control system.
    Attached Files
    Paul Nugent
    Webmaster http://S2central.net
    Administrator http://S2forum.com

    1994 S2 Coupe ABY - aka Project Lazarus
    2001 A6 allroad 2.5TDi - family tank
    2003 S4 Avant 4.2 V8 - daily burble

    Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

    There are only 10 kinds of people that understand binary - those that do, and those that don't

    Comment


    • #3
      A good number of solenoids are apparent on the PCB - all the contacts appear nice and clean - although some signs of moisture are apparent on legs of some components in here. Joints all seem sound enough. For reference this pump carries the part number 4A0 862 257C and does not have alarm/immo capability. This one is made by Hella - others of same era are made by VDO (en Suisse if you please).

      Anyway - out with the pump and desolder its two flying wires for a quick test on a 12V bench supply - motor pumps just fine with +ve on red wire and then sucks plenty well with +ve on blue wire.

      You can see how the pneumatic feedback works - when creating sufficient pressure one pair of contacts is closed by the control valve, whilst under sufficient vacuum another contact pair is closed.

      I'll need to create a test loom for the 12-pin plug so as to test the controller properly someday. These things are fairly low tech... I'd like to retrofit the later variant if possible which can offer comfort features on the windows, add the immo and bring OBD capability as well. Not exactly high on the priority list of course.
      Paul Nugent
      Webmaster http://S2central.net
      Administrator http://S2forum.com

      1994 S2 Coupe ABY - aka Project Lazarus
      2001 A6 allroad 2.5TDi - family tank
      2003 S4 Avant 4.2 V8 - daily burble

      Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

      There are only 10 kinds of people that understand binary - those that do, and those that don't

      Comment

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