Key fob microswitch repair?

Discussion in 'Gen 2 Prius Main Forum' started by Moshy, Jan 29, 2023.

  1. Moshy

    Moshy Junior Member

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    My key fob unlock button has been getting more unreliable, sometimes taking many attempts before unlocking the car. It still locks it fine. I know it's the fob as my spare (now my main fob) still works. I suspect the contacts inside the microswitch on the circuit board are dirty, and this was confirmed when I trickled a drop or 2 of contact cleaner into the gap between the button and the body. This cured it for a while but its got bad again. The switch still clicks fine but there's a poor connection inside.
    Has anyone successfully replaced these microswitches? Or opened them up to clean the contacts? I have a soldering iron but am a novice, plus the 4 little blobs of solder, 1 in each corner, seem mainly to be hidden underneath the switch with no pad on the underside, so if I got the switch off I'm not sure how to reattach it.
    Looking to do a low budget repair if possible.
    Many thanks
     

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  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Those 4 blobs of solder are it- break those bonds and the switch comes off. You'd wick it out with a copper mesh until it finally popped off, very basic desoldering technique just made tricky by the small scale.

    On the other had, most people would just go on eBay and buy a replacement key fob. They aren't that expensive for some models, more for others. I don't happen to know for that one.
     
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  3. Todd Bonzalez

    Todd Bonzalez Member

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    You can get the switches on eBay for £3. Or if you're not up for soldering, you can get a non-SKS B21TA key for around £50
     
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  4. RemiX

    RemiX New Member

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    You can try using a soldering iron but you will likely have to use a reflow machine for something this small. Tried repairing a Samsung phone with a bad volume switch once upon a time, even bought the machine and everything (get 'helping hands' if you do go that route - its a little base with a magnifying glass and alligator clips for small electrical jobs like this). Had a hard time getting it to put out enough heat and managing something that felt like I was missing several hands. That S3 or whatever it was is now forgotten in a bin somewhere.
     
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  5. Moshy

    Moshy Junior Member

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    Thank you for all your replies, most useful.
     
  6. Moshy

    Moshy Junior Member

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    Has anyone attempted to open one of these microswitches?
     
  7. Todd Bonzalez

    Todd Bonzalez Member

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    Nah, you'd need a microscope and they aren't user-serviceable anyway

    There are loads of key repair services on eBay if you don't mind sending the key away for a few days:
    https://www.ebay.co.uk/itm/330515323903

    Or if you buy the switches from eBay, you might be able to get your local phone repair shop to fit them?
     
    #7 Todd Bonzalez, Jan 30, 2023
    Last edited: Jan 30, 2023
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  8. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    yeah the switch itself would be miserable to repair. Replace the component or replace the fob.

    It won't be hard to find a replacement switch, but it may be tricky to buy fewer than 10 of them and still have to pay an outsized shipping charge.

    Maybe harvest a working one from a discarded fob? many will use the same switch. If you harvest the "alarm" switch from another fob it won't have as much wear as the "unlock" switch.
     
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  9. mr_guy_mann

    mr_guy_mann Senior Member

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    If you don't have experience doing surface mount soldering, I recommend you don't try this repair (yet).

    You are going to make mistakes while learning, that's part of life. Mistakes while soldering often means damaged components or boards. You want to practice on scrap boards first. Also having some "specialized" gear helps.

    Might make more sense $$$ to get a replacement fob.

    Posted via the PriusChat mobile app.
     
  10. Moshy

    Moshy Junior Member

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    Wise words, thank you everyone.
     
  11. drone13

    drone13 Active Member

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    My best advise is to buy a key fob from ebay for $40 and also buy a switch (if you can identify and source the part). Get the new key fob working, so Bob's your uncle there. Now try to fix the old one. For a $3 part, why not give it a go and see how you do. BTW, there's no guarantee that the switch is bad unless you have verified the switch doesn't even click, or stays down when pressed, or something very obvious. Hard to tell from the pics, but it doesn't look like it's stuck down. It could easily be something like a bad capacitor, resistor, diode, etc. So yeah it's a bit of a $3 gamble, but what you'll get from that gamble is experience which is bound to be handy at some point in the future.

    So best case: you wind up with 2 working fobs and experience on how to program a fob. Worst case: you wind up with 1 working fob and some cheap experience in electronics repair.

    Definition of experience:
    Experience is what you get when you don't get what you thought you were going to get.

    Good luck
     
  12. Moshy

    Moshy Junior Member

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    You are right the button isn't stuck down and seems to click perfectly normally.
    I really appreciate the suggestions, and hope others will benefit from this thread, but I know my limits- this is '5 spanner' stuff and I'm definitely a 1 spanner kind of guy.
     
  13. ColoradoCrow

    ColoradoCrow Active Member

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    There is a guy on the Range Rovers.net forums who repairs microswitches in the door lock mechanisms who lives in the UK and NZ a few months out of the year. MARTYNZ. However those microswitches are larger than the ones in the key fobs. If you have it that apart. I would spray a lot of electrical contact cleaner under and into the switch itself. If it is not sticking but is still temperamental there could be hairline or small cracks in the actual plastic of the PCB. This is similar to the PCB Boards under the Bonnet in the Fuse Box on the P38A 2nd Gen Range Rover. The soldering joints can be redone but it is large task for a novice solderer. I resorted to buying a new fuse box for $272 and replacing the entire thing. Given what you have already tackled I think a new fob purchase would be your best bet. Plastics just weaken over time and with many presses of the buttons. the fobs just wear out. Les at Rover Connections is THE last hope for us old Rover guys.
    At least you Can still buy new fobs from Toyota.
     
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  14. pasadena_commut

    pasadena_commut Active Member

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    The repair shops for cell phones could replace that switch for you. They have the proper equipment for removing and soldering in a new one. But they may not have a compatible switch in stock. Why not call a couple of shops and find out? Thing is, they might want $80 for the work.
     
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