I have two key fobs that degenerate over time and eventually get to the point that neither button will lock/unlock the doors or hood latch.

Replacing batteries does not help, but it seems that resoldering the IC chips will fix the problem - at least for about 6 months and the problem returns.

After three iterations of resoldering both of these key fobs I am beginning to believe that the problem is related to RoHS requirements where lead is no longer allowed in solder for commercial electronics.

Unfortunately, without lead solder grows what are known as tin whiskers between the legs of ICs and other closely spaced components. The whiskers will eventually short out adjacent pins or create a resistive bridge.

I have been adding solder flux to the IC legs and resoldering them with a tiny pencil iron, then washing the PC board with acetone.

Every time I do this the key fob works like it is brand new, leading me to believe the problem is due to dendrite growth or whiskers from the lead-free solder and IC legs. Next time it starts to fail I will try to put these under a microscope and see if I can image any whiskers.

Resoldering is not for the faint of heart as the lead spacing for these chips is really small. I use copious amounts of flux to prevent solder bridges.

Unfortunately, there is no cure for the whiskers and such is the fate of all modern electronics built to the RoHS standards. Eventually, we will see the ECUs and other electronic modules start to see failures in as little as 10 years, but 20 years is probably more the average. It's just something we have to live with with modern electronics in today's throw-away society.

 

Mine started acting up the other day at high elevation. When I returned to sea level, all good again. Interesting

 

Lead free solder requirement only applies to solder that comes in contact with water.

From the link:

http://www.wateronline.com/doc/are-y...lead-free-0001


The clock is ticking, counting down to the new “lead free” mandate, effective Jan. 4, 2014, which will be considerably stricter than the current federal requirement. Under the Reduction of Lead in Drinking Water Act, signed Jan. 4, 2011, “lead free” will be redefined as “not more than a weighted average of 0.25% lead when used with respect to the wetted surfaces of pipes, pipe fittings, plumbing fittings, and fixtures.”

What “Lead Free” Really Means

Although “lead free” still doesn’t mean completely free of lead, 0.25% (0.2% with respect to solder and flux) is a far cry from the current definition of 8.0%. Semantics aside, the repercussions of the altered definition are significant. Come next year, it will be illegal to sell or install products that do not adhere to the new requirement.

Wetted parts include meters, expansion tanks, backflow preventers, flexible connectors, strainers, and assorted gauges, fittings, valves, etc. — any product used to convey water anticipated for human consumption. Wetted components for nonpotable services such as manufacturing, industrial processing, outdoor watering, or toilets are therefore exempt. But in the case of the former, there is much work to be done.

What I think is going on in your case is the key module circuit is getting in a goofy state.

This can be "fixed" by taking apart the key head and removing the battery and inserting the battery into the socket the wrong way. Plus to minus, minus to plus.

This only needs be done for a brief amount of time. But I have actually pressed one of the buttons to ensure the circuit is entirely devoid of any residual electrical energy.

Afterwards remove the backwards installed battery and install it the right way around and done.

 

That is a different act, RoHS is a European directive that affects all electronics except military and implanted life-critical medical devices.

I am taking back what I first wrote about reversing the battery!

Reversing the battery does not reverse the power, but shorts the B+ to ground. The battery and holder are designed such that accidentally reversing the battery does not fry the components.

Doing this does seem to fix the problem! At least for my spare key. I will keep an eye on how well it keeps working and if it fixes the problem again if it malfunctions again.

Thanks for the tip - much easier than reflowing SMT chips.

 

Glad I was able to be of some help.

 

Thanks for the hot tip. I opened mine and reversed the polarity and now the key works great! Only problem now is that the two halves do not stay snapped together anymore.....damn. I'm now using the other key.... Is there a trick to pulling the halves apart so they go back together cleanly?

 

One of mine is having problems snapping together. I just assumed it was the plastic wearing and deforming.

Just be sure the rubber gasket is not getting pinched.