I recently had a minor win, the key fob for my aging Berlingo was knackered; the buttons would unlock but not lock – which was more than an minor inconvenience when I was with my greyhound Elsie.
I had looked into it before, and I think I assumed there was more damage to the PCB than I thought and/or assumed that soldering on a tiny switch was beyond my skills.
As you can see, the PCB was filthy (because the top side of the fob had fallen apart). Not only that, you’ll notice there is only one microswitch, the should have been one to the right but it’s obviously been knocked off.
Anyway, I did look into replacements but for immobilizers, but this can quickly get expensive. And, because I didn’t have a soldering iron at the time, I discounted a fix.
Fast forward 6 months and I now owning a natty new soldering iron, I revisited this mini-project….
Testing
Firstly I had a brain wave, clean up the board (with iso alc) and then use a wire to trip what I assumed where the ‘lock’ PCB pads.
With this test I could see if the PCB would actually respond properly, saving me the hassle of soldering etc if it was a forgone conclusion.
And yes! It worked! It was lovely to see the car lock actually, as it’s a massive pain to have to manually lock via the driver side door (especially when I’m with Elsie).
New Fob
So, I needed a new small microswitch (or TACT switch I think they are called). I didn’t want to buy 400 so a whole set of them was a pain and then I found the perfect solution, a replacement key fob case that included two switches.
Perfect! I could even test solder one just in case.
Everything arrived and, much to my relief, I was able to solder the switch on without too much grief (yay soldering skills!).
The only issue I had was the I tried to keep the original fob case back with the new front (the bit with the buttons on). The original fob back had a lovely Citroen logo on it.
However, that didnt’ work well as it just didn’t fit very tightly, causing inconsistent button registration plus the whole case opened in my pocket.
So I had to bite the bullet and change out the nice back as well. But I was lucky that I’d just watched a Youtube video on this because, unbeknownst to me, aside from the PCB there is a tiny black transponder in the back of the fob as well. If you weren’t told you would not know it was there! Without know that, the new fob wouldn’t have fully worked. I’d have got there in the end, but I was glad I saw that video.
Anyway, that’s a lot of text to sum up a simple fix; but a fix that I really appreciated; a fully working key fob again!
