Poll: Key Fob Failure Diagnosis

Here’s something new. Let’s bring your collective experience and knowledge to bear on a particular case brought before Made By Monkeys.

key-fob1.jpgHere’s something new. Let’s bring your collective experience and knowledge to bear on a particular case brought before Made By Monkeys.

We recently highlighted a Mercedes key fob failure – please see Key Fob fails for surface mount leads – and lots of pics of the problem are available for inspection. We’ve identified seven possible causes of failure, but what are your thoughts? Multiple answers are possible, and feel free to suggest Other causes.

Key Fob Failure Diagnosis – What do you think went wrong?(surveys)

If you have any suggestions for future Made By Monkeys polls, do leave a comment below.



  1. My key fob was only starting my mercedes on about the 20th to 100th time or sometimes even an hour of effort. I would put it in the ignition. I thought the problem was that the lens on the tip of the fob was scuffed up and therefore not letting the infrared through. I refuse to pay mercedes for their poor engineering so I decided to fix the fob myself. I tried to polish the surface of the lens but that made it worse so I very gently ground the tip of the fob down a little on my bench grinder and then when the lense was thin cut it completely away with exacto or pocket knife then You can see the 2 infrared senders. Turns out because the alarm arm push button was cracked there was pocket lent that built up over one of the sender units. I picked out the fuzz and what do you know, starts every time. I put a clear piece of box tape over the end of the fob and now put the key in a small ziplock bag before I pocket it

  2. Thanks Justin. Those critical exceptions do always seem slightly damning for the case for lead-free solder…
    I think eco-friendly alternatives have to reach, or surpass, existing qualities. I’m thinking particularly of some of these engergy-saving lightbulbs that are slow to start and fill a room with gloom. Is that really the green alternative? Surely, with the likes of LEDs for example, we can do better AND be environmentally conscious. If people think they have to settle for second best they’ll do their best to avoid the option. Like with people trying to hoard supplies of old solder…

  3. ROHS approved lead free solder makes much poorer joints than the old fashioned kind and it doesnt get used for MILSPEC or space qualified work because it is vulnerable to cracking under vibration.

  4. Re Merc keyfobs. This problem has been about for some years. A friend showed me her keyfob which had failed, this was about 4 years ago. It took 3 minutes to fix with a bent paperclip acting as a switch to fix it. It is still working in 2009. Simply a case of poor design of a switch which will be used 100’s of times.

  5. Sure, glue may have helped reduce the mechanical stress on the joints, but in my experience the surface-mount soldering of plugs/sockets/switches in CE is frequently poor.
    There is possibly a problem of insufficent heat in soldering for the large mass of metal in the switch/socket leads, and/or the switch/socket leads are oxidised so make poor joint from day 1. This may relate to insufficiently active flux, or partly just due to lack of heat.

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