Saving and re-using glass parts for re-installation
Advances in auto glass systems and technology pose many challenges for auto glass technicians. Vehicle manufacturers use “exposed edge” or “naked” glass and flush-set designs to create a distinct look, address water-management issues and provide sleek aerodynamic styling. One of the biggest challenges facing technicians today is the successful removal of encapsulated glass; glass with a Pre-Applied Adhesive System, or PAAS, design; and glass with underside molding for re-installation later. During glass removal, technicians can potentially damage any of these molding systems beyond repair and make them useless for re-installation. Purchasing a new glass part was the only option for a long time, until universal underside replacement moldings came along.
Moldings used to be metal and held in place with clips that attached to rivet studs on the vertical wall of the pinchweld. Technicians used a special clip or molding tool to release the clip from the molding prior to removal. If the installer was not careful, he or she could easily scratch the paint near these clips, leading to potential rust problems.
Vehicle manufacturers began to incorporate encapsulated parts into their designs in the mid- to late-’80s to speed up the installation process, address the paint issue and reduce vehicle weight and cost. However, after several years in the field, it was determined the encapsulation might have caused de-lamination. As designers moved away from encapsulation, they continued to look for a less expensive way to make glass parts.
Enter glass parts with no external moldings or “naked” glass. These parts addressed design challenges, the placement of the glass to maintain aerodynamic flow around the vehicle, wind noise and installation time.
Manufacturers introduced PAAS, an alternative manufacturing method that uses an extruded bead of urethane to form a finished perimeter trim around the glass. This system allowed technicians to set these module glass parts to the proper height and simplified the installation process.
Techs can use underside trim or moldings to finish off an exposed-edge glass part and maintain correct height. These moldings can be made from several materials: EPDM, closed-cell foam and polyvinyl chloride, each with a specific use. EPDM and PVC products are best suited for mitered corners, while closed-cell foam has the ability to wrap neatly around radius corners. These systems are used on windshields, back glasses and quarter glasses.
Tips and techniques
Technicians now have options to save and re-use glass parts for re-installation. Consider the removal of a rear window from a 2000-05 Ford Taurus. If cutting from the inside, technicians must remove interior trim to gain access to the urethane. If the encapsulation is damaged to the point where it is visible on the exterior, it might not be acceptable to the customer. Using an underside replacement molding with the correct fin length, technicians can now remove the old encapsulation, clean and prepare the surface according to the urethane manufacturer’s specifications and apply the replacement molding; cut the molding to the proper length, miter and glue, or fuse the two top corners and re-install the part. The molding can be glued at the mitered joint with specially formulated ultraviolet-resistant glue if it is an EPDM product, or heat-fused if it’s a PVC material.
Glass parts with radius corners like the Suzuki Forester quarter glass windows use closed-cell foam underside moldings. They apply easily and take up limited space on the perimeter of the glass. Check for minimum bead bonding requirements.
While the adhesive tape on an underside molding firmly holds the molding in place as the technician prepares the urethane and glass part for installation, remember that the tape is not enough to hold the glass in place and does not meet Federal Motor Vehicle Safety Standards. If your urethane manufacturer recommends a primer for the type of molding you are using, use it.
Some other tips to remember:
• Always make sure your bonding surfaces are clean, dry and primed if required.
• Run a V-bead of urethane overlapping the molding and glass.
• Prime any required surface.
• Check with the urethane manufacturers’ guidelines and the Automotive Glass Replacement Safety Standard.
• It is important to make sure you have the minimum urethane footprint requirement on the glass and pinchweld.
• If you purchase glass without underside moldings, use one of the molding types mentioned earlier and apply to the part.
It is up to the technician performing the task to determine whether the methods mentioned in this article comply with accepted installation practices.