2006 Hyundai Elantra Key Fob Case Replacement

Update: April 10, 2023

It's been about three years since the original design, and the button, printed with flexible PLA in the original design has crumbled to tiny pieces. Time for a design re-think!

...so, I've created an updated version that only uses "standard" PLA for the entire thing.

I also took the opportunity to...

• better align the lock button position with the circuit board - it worked fine, but the positioning was a couple of millimetres off
• clarify the battery orientation indicator in the key fob base (positive sidedown!)
• fill the hole for the LED indicator (you don't have to fill anything with glue now) - there's no need for a hole there in the first place, since the PLA in that location is thin and translucent enough that you can easily see the indicator light through it.

For this new version, use the following STL files:

• key-fob-button_10-04-2023.stl
• key-fob-base_10-04-2023.stl
• key-fob-lid_10-04-2023.stl

...and just print everything with normal PLA.

The assembly instructions are the same as before (apart from the bit about the glue, which you can skip now). Refer to the instructions below (and the photos) for more details.

2006 Hyundai Elantra Key Fob Case Replacement

Why?

The key fob case on both key fobs I got when I bought the car were starting to crack and fall apart in the exact same way (see the photos).

Given that the car was almost 15 years old at the time, I wasn't overly surprised, but when I called up about the cost of replacing the fobs I was told they were in the region of A$450. Each.

Not wanting to spend close to A$1000 to replace them, I instead bought a cheap 3D printer with the intention of replacing the case (since everything else was fine) with one of my own design.

Yes - this problem is the reason I bought a 3D printer.

How much did it save me? By my reckoning (ignoring the time spent designing and working out the kinks), about $700 in the clear. Take that, key fob industry!

What?

There are three parts to the print:

• the front and back of the case in PLA
• the button in flexible PLA.

You will also need...

• four 8mm M3 screws and nuts - the ones I used have a hex key bit rather than screwdriver bits, so the heads are quite tall. If you are using screws with more traditional Phillips heads you might well get away with 6mm.
• a scrap of kitchen foil for the bottom battery contact
• a tiny amount of superglue to make the "window" for the LED indicator light to improve water resistance.

How?

First print the parts, and then just quickly do a test by pushing them all together and making sure it all fits - the friction fit between the two half of the case should be quite tight, and hold itself together nicely.

Next, before doing the final assembly, put the screws and nuts in and screw it all together as if it were the final assembly. The case is designed for the screw heads and nuts to sink into the case, but the fit is quite tight - just screw it all together first to get all of that in place - the nuts on the bottom should wedge in place, and then you can remove the screws.

Grab the kitchen foil scrap and press it into the bottom half of the case where the battery compartment is with your thumb, and lift it out again. Use the impression made in the foil to cut it out to the right size, and then place it in the bottom half of the case. Make a second thin piece to go from the base and up the "ramp" to the top contact point to ensure a good connection with the circuit board.

Put the battery in place (positive terminal is downward, as indicated in the case itself).

Grab the circuit board, and place it with the chips etc upward on top of the case, oriented with the LED indicator endaway from where the strap attachment is.

NOTE: If you are using the 10-04-2023 version, you don't need to do this next bit with the glue

Get the lid, and mix up a small amount of superglue -NOTE: this isn't to stick the key fob together!

Using a toothpick or similar, dip it in the superglue and fill the tiny hole in the lid with a small amount of glue. This will create a water-tight transparent window for the LED to shine through so you can see it flash when the buttons are pressed.

Wait for the super glue to set, as per directions on the packet of whatever brand you are using.

Next, fit the button to the lid, and then fit the halves together.

Holding it together with your fingers, do a quick button press test to make sure that it works. I haven't had much trouble with this, but if it doesn't work...

• make sure that nothing has shifted inside
• that the battery is in the right way
• the kitchen foil connection is alright
• check everything is in its place and the right way around

Once you're satisfied that it's all good, do up the screws nice and tight, test again, and you're done!

Print Settings

Printer Brand:

Anet

Printer:

A8

Rafts:

Doesn't Matter

Supports:

No

Resolution:

0.1mm

Infill:

20%

Filament: 3DFillies PLA, PLA Flex

Orange, Black

Notes:

• I printed it in orange, because that was what I happened to have in the printer at the time I did the final prototype. Initially I planned on doing it again in a more stylish black, but after printing I quite liked it for some reason, and it has the advantage of being easy to spot at the bottom of a bag or purse. The final colour is up to you of course!
• The fit is tight enough that I think it's reasonably water proof, or at least (I hope) as waterproof as the original keyfob was, especially with the "superglue window" in place for the LED indicator. It's certainly "splash proof", and would handle getting wet in "normal use cases", such as unlocking the car in the rain etc. That said, I wouldn't go deliberately dunking it in the pool or going SCUBA diving with it.
• I used superglue for the LED window, but presumably there are alternatives if this doesn't appeal to you for some reason.
• In my experience, the button really needs to be printed with a flexible material, otherwise when you push one button down the other also tends to jam down. Probably this could be solved by printing the button as two separate pieces - this is left as an exercise for the reader. (Update April 10, 2023: as noted above, there's now a 100% PLA only version that side-steps this requirement).