Hello all,

I have an 2009 BMW 520d non comfort access, and I've been having problems with my key.

The whole key works but my problem is that the unlock button is so sensitive that as much as resting your finger on it will unlock the car, sometimes I lock the car, put the key in my pocket and leave to go somewhere for a couple of minutes and come back to my car open and all the windows down.

Any ideas of what it could be? I thought it was the shell casing but i changed it and it still does the exact same thing.
Thanks in advance. ​​​​​​

 

Sounds like the micro-switch inside is messed up. If you already had the casing off, take it off again and just fool around with the micro-switch and see if it is hair trigger. That might be a broken spring element inside the switch. Depending on how the switch is constructed, that may be a discrete spring or is may be a shaped piece of metal. Assuming this is the issue, you should be able to source a compatible switch and have it removed and soldered in.

 

Is it a hard job to do by myself? I was able to replace the battery with a soldering iron but the button is much smaller and I couldn't find a video tutorial anywhere. Could a phone shop be capable of doing it?

 

It is probably a surface mount switch and that is going to be difficult for you to do yourself unless you have some higher end soldering stuff and experience. Yes, a phone shop can probably accomplish this.

I don't know the electronics parts mail order in the UK, but in the US, I'd be looking at digikey.com and newark.com to find the switch or cannibalize it off another BMW key I got off eBay or something like that. Or, I just found this located in the UK and it may be exactly what you need:
https://www.ebay.com/itm/282353238919