Athermic Glass (also known as Heat-reflective, or solar glass, or solar control, or infra-red interlayer) can impact on the performance of your radar detector, GPS detector or portable GPS navigation unit.
It's basically a very thin layer of metallic content that is laminated into the centre of the windshield, so it can reduce radar detection range to the front and can make your GPS device take much longer to get a satellite lock. It can also mean your toll transponder can't be read.
The solution is to find the "clear spot" in the windscreen that manufacturers normally leave, often behind the rear view mirror area, or to consider a custom installed "remote" radar detector system. Use a pair of polarized sunglasses and if should be clearly visible.
This picture (Great spot by euro - €) shows you it clearly.
If you have GPS performance issues, then most manufacturers sell an extension antenna, which you can run to the back window, or to the outside of the vehicle.
A more drastic solution is to have an "accident" with the windscreen which requires an aftermarket replacement.
Vehicles confirmed with Athermic windscreens include:
Aston Martin Rapide
Audi A8 ('06 +)
Bentley Continental GT (all windows except a 2 inch strip at top of rear window)
BMW 7 series
BMW 6 series
Buick Rendezvous CXL 2003
Buick Roadmaster (some '90s models)
Cadillac Fleetwood (*possible)
Chevrolet Caprice "Fourth Generation" (1991-1996) - (*possible)
Chevrolet Corvette (some late-80s/early-90s models - look for a red-bronze tint)
Chevrolet Impala SS (some '90s models)
Chevrolet Lumina minivan ('89 - '96)
Chevrolet Venture ('98 +)
Citroen (French car - all models '01 +)
Dodge Durango (06)
Ford Focus (UK Spec '05 +)
Jeep Commander (Deep Tint Sunscreen Glass)
Jeep Compass (Solar Control Glass or Deep Tint Sunscreen Glass)
Jeep Grand Cherokee (Deep Tint Sunscreen Glass)
Jeep Liberty (Solar Control Glass or Deep Tint Sunscreen Glass)
Jeep Patriot (Solar Control Glass or Deep Tint Sunscreen Glass)
Jeep Wrangler (only a problem on a few vehicles that were fitted with the optional extra Deep Tint Sunscreen Windows. Most Wranglers only have the normal Tinted Windshield Glass fitted as standard and that does not cause issues.)
Mercedes A Class ('08 +)
Mercedes S Class ('08+)
Oldsmobile Silhouette ('89 - '96, 98+)
Peugot (French car - all models '01 +)
Pontiac Trans Sport ('89-'96, '98 +)
Renault (French car - all models '01 +)
Vauxhall Zafira (UK)
Please add in other vehicles and I will edit this original post to as the list grows.
Ford vehicles can be equipped with InstaClear windshields. This is a different thing to Athermic glass and does not affect radar and GPS as much, but it does have a lot of metal filament embedded into the glass so it's worth recording here and it can have a slight negative impact on performance. Ford didn't start using Athermic glass on some models until 2005, but here are some of the Ford Models to watch out for:
Ford Taurus (optional InstaClear windscreen - look for a bronze tint)
Lincoln Continental (optional InstaClear windscreen - look for a bronze tint)
Lincoln Town Car (optional InstaClear windscreen - look for a bronze tint)
Ford Crown Victoria, "First Generation" (1992-1997) - optional
Mercury Grand Marquis
Mercury Sable (optional InstaClear windscreen - look for a bronze tint)