My GPS would lose signal in the same three spots on my commute every day. Not in tunnels — just regular surface streets with normal buildings. It would freeze, recalculate, and suddenly I am apparently driving through a lake according to the map. I thought my phone was dying.

Turned out it was my windshield. Specifically, the metallic coating on my aftermarket windshield was blocking the GPS signal like a Faraday cage.

Why GPS Fails in Some Cars

Many modern and replacement windshields have a metallic oxide coating for UV and infrared heat rejection. This coating reflects radio waves — including the roughly 1.5 GHz signals GPS satellites broadcast. Some cars also have heated windshields with embedded wire grids that further block signals.

Your phone or GPS unit is trying to hear whispers from satellites twelve thousand miles away, and your windshield is basically screaming into its ear.

The Tin Foil Reflector Trick

GPS antennas are directional. They receive best when pointed at the sky. If the direct path through the windshield is blocked, you can sometimes reflect signals around the obstruction:

1. Take a piece of aluminum foil about the size of a sheet of paper.
2. Fold it into a shallow curved dish shape — like a tiny satellite dish.
3. Place it on your dashboard with the concave side facing upward and slightly toward the windshield.
4. Set your phone or GPS unit in front of it, with the top of the device facing the foil.

The foil reflects GPS signals that come in through the side windows and bounces them toward your device. It is not a miracle fix but it can boost a marginal signal enough to stop the dropouts.

Better Long-Term Solutions

• External GPS antenna. Some dedicated GPS units have a port for an external antenna you can mount outside the car. This is the real fix.
• Phone mount on the side window instead of the dash. Gets the phone out from behind the coated windshield.
• Update your maps for offline use. If GPS drops in the same spots, having offline maps means navigation still works — it just loses the moving dot temporarily.

The foil trick helped me through a road trip before I figured out the windshield issue. It looked dumb. A shiny foil dish on my dashboard. But my GPS stopped routing me through lakes, so I will take the win.