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How to fix a key fob

While the button contacts in virtually any fob can wear out, the fobs used by many GM models also have a common internal failure that can render one button or the entire remote non-functional. It’s a pretty easy fix.
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Unless you own a car that’s old enough to vote, you’ve got a keyless entry fob.

These remotes, even the proximity-style and push-button start fobs, all use batteries that occasionally require replacement. It’s the most common reason for fob failure.

While the button contacts in virtually any fob can wear out, the fobs used by many GM models also have a common internal failure that can render one button or the entire remote non-functional. It’s a pretty easy fix.

There are a few things that are known to go wrong with these remotes — however it must be said that they tend not to fail outright without experiencing some kind of trauma.

 

Getting in sync

The contacts inside the buttons do wear out — obvious if wiggling or squeezing the buttons sometimes make it work.

If the remote has been inoperative for a long time (i.e. dead battery), you may need to resync it by holding the “Lock” and “Unlock” buttons simultaneously for several seconds.

The most common failure is the one we’re going to fix.

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Split it up

There are several ways to access the battery in fobs and remotes. Some use one or more small screws, some have a battery door, others require partial disassembly. There’s normally a slot suitable for a coin, screwdriver, or even kitchen knife to be twisted to separate the halves. If there’s no slot, carefully use an appropriate tool to wedge them apart.

Open it over a proper work surface like a table or workbench, as there may be a small loose part inside that we’re going to need in a moment.

Bridge the gap

With the fob split open, we can see the circuit board and battery. If you look closely near the centre of the photo, you can see that the metal clip that holds the battery is not sitting where it is supposed to.

The metal tab not only holds the battery in place, it is also the positive conductor for the remote. Where the two small tabs go through the circuit board, they connect to the board’s wiring. If just one breaks off, it may only affect one button.

Erase the problem

With the clip removed from the remote, it’s easier to see the small metal fingers on it that protrude through the circuit board. These tabs are also under spring pressure when the battery is installed, as the central “finger” presses the battery down to hold it in place and create electrical contact on both the top and bottom.

The grid visible on the board is the negative contact. It touches the central part of the bottom of the coin cell. You can use a pencil eraser to clean both this and the similar-looking button contacts on the board’s reverse side.

Heat it up

When soldering, there are a few points to keep in mind. First, electronics don’t like excessive heat, so exercise caution with the iron. Heat the tab and melt the solder on it, not the iron. Ensure that the tab is hot enough that the solder flows into the holes and the depression on the board. Also, don’t use too much solder, and be sure to use solder intended for electronics, not plumbing. I prefer a 1 mm diameter rosin core.

Ready to go

This is not the prettiest repair I’ve ever done – don’t take photos while soldering. The fob had been fixed, however, and should remain so. Full function was restored, and the owner was very pleased not to have to choose between the cost of replacement and reprogramming or losing her keyless entry feature.

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