Introduction: Exorcising a Haunted Key Fob

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first to…

This is the key fob for my 2012 Hyundai Sonata in the key wallet I usually carry. Hyundai owners with this key fob sometimes find the trunk on their cars opened by itself, as if haunted. There is a lot of discussion about this problem on owners' forums. Some are certain it is caused by an electrical anomaly in the car's systems or by interference from a stray radio signal. One man carried his key fob in a separate hard case and never had an occurrence of the trunk opening by itself during that time. When he carried his key fob in a wallet, his trunk sometimes opened mysteriously. See the text boxes on the photo. I have found my trunk opened by itself about four times. Each of those was while the car was parked in my garage. I think the little button that is part of the wallet clasp may have exerted pressure on the trunk button on the key fob. This Instructable will show how to make a hard cover for the key fob that still allows easy access to the fob for use.

Step 1: What Is Available Commercially

These key fob covers are available in various colors for about $9 US each. I decided to make my own key fob shield from the cover of an old computer power supply. (The image is from Amazon. To view product information, follow the link.) Tools
  • Metal shears or snip
  • Marking pen
  • Ball peen hammer
  • Stack of newspaper
  • Drill
  • Grinder
  • Needle nose pliers
  • Wire feed welder (unless the non-welded version is chosen)
  • Light gauge steel from a computer power supply case, or something similar

Step 2: Pound to Fit the Fob

Auto body people have a leather bag filled with lead shot. They place a piece of sheet metal on it and pound with a hammer to make rounded indentations in the metal surface. I used a stack of old newspaper on top of my workbench and a ball peen hammer. I pounded a recess into the metal sheet to fit the contours of my key fob.

Step 3: Mark for Cutting

I used a fine marker pen to outline the key fob on the metal. I did some additional pounding to fit the outline of the fob. I marked straight lines at the bottom end of the fob. The piece defined by these lines will fold upward and around the bottom end of the fob to keep my shield on the key fob when it is in my key wallet.

Step 4: Cut

I used a metal snips to cut as near to my marks as possible. Later I will grind and file to smooth the lines. The snips always deform the metal. I pounded it flat after cutting.

Step 5: Bend

I bent the tabs upward. These will fit around the bottom end of the fob.

Step 6: Fit and Tack Weld

I used a needle nose pliers to fit the tabs around the bottom of the fob and tack welded each with one weld. Adjust the fit and add additional tack welds. I did not weld every bit of the joints, but only most of them. I also trimmed the tabs so both were the same length. 

If you do not have access to a welder, you could make a version of this without welding. Follow all of the steps up to this point, but plan to use tabs according to the second graphic shown with this step. Then bend them. Round and smooth any rough edges and corners.

Step 7: Additional Details

In the photo I have finished the welding and ground the welds smooth. I drilled a hole near the top of the fob shield for the holder in my key wallet. I filed and ground away any rough edges. I also used a flap disc to make the appearance a little prettier.

Step 8: Finished

This is how my fob shield looks when it covers the fob. I will need to practice using it so I can smoothly remove it to operate the buttons on my key fob. But, it covers the trunk button and the others fully so nothing can press on them, as would still be possible in the commercial version shown in step 1.