This week's tip:

It's a given today that metalized film may interfere with AM radio reception in the event the antenna is located on the back glass. The phenomena of quasi-connecting the antenna to the defroster grid (which grounds the signal to the chassis) after installation of metalized film to the back glass is believed to be part of the problem. This tip is NOT for other electronics such as GPS, XM radio, Wi-Fi, Cell Phone, etc., which are affected by the RF shielding capacity of a metal film.

Locate the uppermost defroster line (this would be the last of many that travels completely across the back glass with no breaks in its line). Carefully cut a seam into the film, either before or after installation, running above, parallel and adjacent to the uppermost defroster line (not the antenna line). This breaks the quasi-connection and grounding effect between the film, antenna and defroster grid.

If this does not work, you may have to resort to extreme measures: 1) Cut another seam BELOW parallel and adjacent to the uppermost defroster line and remove the sliver of film from that particular defrost line. 2) R & R with a non-conductive film construction such as straight-dyed, pigmented polyester, IR absorbing film or a combination of these.

I have even had a consumer ask me to remove a sliver of film over the entire antenna line, which for that vehicle was an upside down T and easily done. Other more elaborate antenna grids would be most difficult and time consuming.

Of course, the consumer should be consulted and advised as to the trade off between radio reception, film performance, and 'possibly' looks (In this day and age of one-piece installs).