How to repair a faulty 2.0 16v ABF throttle close microswitch

Discussion in '16-valve' started by Mk2daz, Mar 9, 2020.

  1. Mk2daz

    Mk2daz Paid Member Paid Member

    Jun 2, 2015
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    I recently converted my mk2 scirocco to run a 2.0 16v ABF on standard management, the car is now my daily driver which unearthed some strange idling woes.

    When the car was run up to temp i was finding that the idle was sometimes sticking quite high, sometimes even as high as 3k, or it was jumping between 500 and 3k rpm - not ideal when your sitting at red lights..

    What i found was that the throttle stop microswitch was faulty. This switch is responsible for feeding back to the ECU wether the throttle is fully closed or not, in which the ECU will adjust the amount of fuelling etc accordingly.

    The switch is located on the back of the throttle body and has a two pin plug going to it (its worth also checking these two wires for breaks before you test the switch as they can get brittle with being so close to the hot manifold!)

    To test the switch, simply put a multimeter across the two pins and set it to continuity (or resistance).

    What you want to see is O.L. (open loop) when the throttle is open and some kind of small resistance reading when the throttle is closed.

    in my case i have an open loop even with the throttle closed = faulty switch.

    The original switches are very very hard to get hold of now, and theres not much point either, they will be just as old as your current one, these are just basic microswitches, and so replacing with a generic one will work just as well.

    Here is the switch i purchased to replace the faulty one - credit to Mr @rubjonny for providing me the link

    RS components, less than £3 delivered next day!

    SPDT-NO/NC Hinge Lever Microswitch, 100mA @ 30V DC

    Also credit to @BISSONE for his original thread on repairing the micro switch from which most of this info comes from -

    Step 1 - remove the silicon/potting compound that protects the soldered joints by heating it up with a heat gun and scraping it out with a stanley blade or thin screwdriver, keep doing this until you find the two terminal legs from the 2 pin plug.

    Step 2 - prise out the faulty switch trying not to break the two support pillars that hold the switch straight in place. In my case one of them broke, if they both break then BISSONE has a pretty nifty way of creating new ones.

    Step 3 - press in the new switch, i used some super glue here to hold in firmly in place.

    Step 4 - solder the switch pins, i have a cheapo soldering iron that cost me about 15 quid from ebay

    Step 4 - verify that the switch is working, repeating the same tests with the multimeter
    49638470148_bcb5c66e39_k.jpg 49639270647_19f4d73d29_k.jpg

    Step 5 - protect the soldered joints with potting compound if you have, or some silicon will do, in my case all i had was some grey silicon - this will work perfectly fine

    Step 6 - In my case the switch had came away from the bracket that is bolted to the throttle body, i used some super glue and some tiger seal to secure it back on, looks a bit messy but once the silicon etc sets and hardens it will look better - who cares anyway, as long as it works!

    Step 7 - refit to the car and ensure when the throttle is closed that it engages the microswitch and you hear a click.

    Step 8 - fire up the old girl and give it a test ;)

    So far so good for me, on the commute to work when the car has got up to temp i have experienced no strange or high idling, so i think the switch is doing its job.

    Cheers - Daz
    Vr6jett, erreesse, HPR and 1 other person like this.
  2. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

    Jul 26, 2006
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    Creating Pfredstarke
    It is not pretty but who cares!

    That is what we like to see [:D]
  3. Tom-uk Paid Member Paid Member

    Sep 23, 2015
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    Nice one, Done the same job myself - £70 for a new used throttle switch or £3 for a generic microswitch off RS, its a no brainer :thumbup:
  4. Mk2daz

    Mk2daz Paid Member Paid Member

    Jun 2, 2015
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    Just an update that this cheap little switch is still working great, my car idles spot on everyday!
  5. MJA

    MJA Paid Member Paid Member

    Dec 30, 2019
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    North Herts/South Cambs borders
    Great find and noted for myself for future reference! I also like your committement to the cause with dirty hands :-D
    Mk2daz likes this.
  6. Mk2daz

    Mk2daz Paid Member Paid Member

    Jun 2, 2015
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    Thanks, and yes, I'd been working on the car all day before taking the pictures! [:D]
  7. rubjonny

    rubjonny Administrator Staff Member Admin

    Oct 31, 2003
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    Just done this myself, the switch listed ended up quite pricey including VAT and delivery as I didn't need anything else from RS at the time, and nothing on ebay for a reasonable price.

    I did some more searching using various other search terms and found a similar switch from the same Cherry DC3 range part number DC3C-K9AA for £3 delivered. Pretty much same switch except it has long thin PCB surface mount pins plus instead of holes all the way through it has holes 'top' side and pegs 'bottom' side from ABF microswitch fitment orientation:

    This actually worked out perfect, as I managed to snap both the mounting pegs off the switch body. So all I needed to do was use a small hand drill to ream out 2 holes where they used to be and the switch pegs fitted nice and snug into them :thumbup: Once the soldering was done I had a bottle of 'liquid insulation' to hand which I used as a substitute for potting compound, bobs your uncle:

    I had a handy blade attachment for my gas soldering iron which cut through the old potting compound like butter, highly recommend:
    harryvr6 and Mk2daz like this.
  8. wone New Member

    Sep 23, 2021
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    thank you

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