Fitting new switches to fob

[sproutdreamer]

I got my key fob wet and it stopped working. It dried out and now works mostly but only with lots of key depressions. I can buy replacement mini switches-are the replacement switches soldered in or do they just clip into the PCB?

[paul9]

Solder. And fiddly, too, especially if you aren't used to soldering small surface mount components. A phone repair shop would probably do the job for you for a small cash fee. Are you sure it's the switches? Flood the thing with electrical contact cleaner, and give it a quick scrub with a cheap toothbrush from your local supermarket. Halfords and Eurocarparts will have contact cleaner. If that doesnt work, then try the switch replacement.

[sproutdreamer]

As I recall you have to be very careful not to get heat flow back to the PCB from the soldering iron where it can overheat components. I will try and find a tiny tip solder iron. I will post back if this is successful.

[Gerg]

On our Mazda, on which the key fob has never got wet, we had surprisingly similar symptoms - the key fob would only work after a great many button operations. 

This was fixed by replacing the fob Battery (!). It would seem that I trying to repeatedly use the fob, the button cell Battery, perhaps through warmth, became active enough to begin to work almost normally. 

Both key fobs ending up doing this. 

New batteries were fitted - all now good. 

When the batteries were spent, I expected the fob to stay useless, regardless of what you did. But heat from the internal resistance of the Battery, or perhaps your hand (less likely) got it sort-of working. 

Anything below around 3.05 volts for the cell, then it needs replacing, even though these batteries are rated at 3 volts. I have found that figure through trial and error!  A new cell is around 3.30 volts. 

I'm sure you've already checked this, but just thought to mention it anyway. 

In my case, I thought the battery was quite new, and had taken the pcb out to look for a dry or fatigued solder joint on a button switch  -  wrong! 

[fordulike]

I used to repair key fobs many years ago and most have a similar pcb and micro switch arrangement.

If you are going to repair it yourself, use a solder sucker in conjunction with the hot soldering iron tip, to remove the micro switch and old solder. Use something like a crocodile clip to hold the new switch in the correct place and then solder the tags. Simple, but can be fiddly, so don't rush it.

[flash22]

Flow the joint with a bit of fresh solder, I have used desolder braid with a little extra flux method for too many years to remember it works 95% of the time, use a good quality braid tho

 

Re. Testing batteries

use a 100 ohm resistor to act as a load this will give the true reading of the cell

[Exvec]

On 8/11/2020 at 7:08 PM, sproutdreamer said:

I got my key fob wet and it stopped working. It dried out and now works mostly but only with lots of key depressions. I can buy replacement mini switches-are the replacement switches soldered in or do they just clip into the PCB?

I have the locking micro switch gone on my key fob and i only have the one key,where did you source the new micro switch from if i may ask.