Nelsonmd
New member
So I have had an intermittent key FOB since I got my 4runner. The lock seems to work fine, but the unlock, and the rear window down button just don't seem to work except maybe 10% of the time. Now I could just get a new key FOB and reprogram the car, but I also can't seem to get my car to enter programming mode, so I am stuck with my one single key FOB. Having to use the key to unlock is really irritating me, so today I thought, I'll just crack it open and have a look see, I design circuits for a living, I should be able to figure out what's wrong.
So I cracked it open, put it under a scope (yay for being an engineer with a small lab in my cubicle!) and lookey what I found:
Tin Whiskers!!!!!!
These are both on the unlock button.
For those unfamiliar with the phenomenon, high tin content metals have this very strange tendency to eject thin, long strands of tin that can reach out and touch other contacts on a board. You would be amazed at the lengths these things can reach, I mean those 2 I had were pretty long. Google it and you will find tons of info.
So I took the smallest probe I had (which was a really really small straight edge jewelers screwdriver) and pulled the whiskers off, and cut them off as best I could. My unlock is now functioning about 75% of the time. Not a complete fix, but I suspect I haven't gotten all the whiskers, or left a stub that is shorting out. The whisker in the first pic was definitely contacting that neighboring resistor, it terminated right into the solder joint. I am going to take a closer look tomorrow and see if I have missed anything.
I have definitely gotten a huge improvement.
So I cracked it open, put it under a scope (yay for being an engineer with a small lab in my cubicle!) and lookey what I found:
Tin Whiskers!!!!!!
These are both on the unlock button.
For those unfamiliar with the phenomenon, high tin content metals have this very strange tendency to eject thin, long strands of tin that can reach out and touch other contacts on a board. You would be amazed at the lengths these things can reach, I mean those 2 I had were pretty long. Google it and you will find tons of info.
So I took the smallest probe I had (which was a really really small straight edge jewelers screwdriver) and pulled the whiskers off, and cut them off as best I could. My unlock is now functioning about 75% of the time. Not a complete fix, but I suspect I haven't gotten all the whiskers, or left a stub that is shorting out. The whisker in the first pic was definitely contacting that neighboring resistor, it terminated right into the solder joint. I am going to take a closer look tomorrow and see if I have missed anything.
I have definitely gotten a huge improvement.
