ALT-3 Auto Glass how to Replace Auto Glass
Windshields:
There are three basic ways that windshields are held in place in any car or truck. Each has advantages and disadvantages based on the use and application it was designed for.
The oldest is called "rubber set" where the glass is secured in a molded rubber gasket. This gasket may be self-locking, may have an insertion locking strip, or be molded such that it must be put on the glass and then "lipped" into the vehicle. This system, which is still used in tractor trailer rigs and some heavy equipment, was designed to allow for a relatively simple means of escape in the event of an accident. Older vehicles did not have fuel shut off switches to prevent fuel leakage and fire; though built stronger than today's vehicles there was a real possibility that the doors might become jammed by impact or captured in a rollover, so the most efficient method of emergency exit was through the windshield. These were designed such that one could use both feet and push the windshield out of the vehicle allowing the occupants to exit safely.
As trucks "came off the farm" and cars became more stylish and sleek, a lighter and more streamlined system was needed for windshields. Butyl tape {some still call it dumdum} began to be used with a metal molding to insure that the windshield would remain in place during an accident. It is from the use of Butyl that the term "tape bed" originated, and is still used today though the use of Butyl is now illegal for some very good reasons that I'll cover in the next section. A windshield installed with Butyl could still be removed in an emergency by "kicking it out", but the general advantages were that there was less leakage and it allowed for a smoother, more streamlined installation.
The windshields in today's cars and trucks are designed to be integral components of the body structure, so the glass must be bonded to the vehicle body. The strength and durability of Urethane fits this requirement nicely. With a sheer strength averaging 1,000 psi or greater, and a lap strength of 1,300 psi or greater, Urethane is the adhesive required by law for every windshield in any private passenger vehicle. A windshield, properly installed, is to stay in place in an accident or rollover. This protects the occupants from being thrown from the vehicle, and provides added structural support for the roof to prevent it from collapsing in on the occupants. If the windshield fails to remain in the vehicle, the probability of injury or death increases 400%. Butyl tape is simply not strong enough to meet these requirements, and is therefore illegal to be used on any windshield; it is however still used on some back glasses that are "bolted in" as opposed to bonded.
Removing the old glass is dangerous work requiring specialized tools for removal, and if the old glass was not properly installed the danger level increases in direct ratio with the installer's lack of professionalism, so beware because you don't know who has been here before you. With the old windshield removed, the old Urethane must be removed to insure a solid and proper installation. At this point there are three items {other than the glass} that you will need; Pinchweld Primer to paint the metal where the old Urethane has been removed, Glass Primer to be applied to the clean replacement windshield, and Urethane. Urethane is the only one of these three parts that you can buy "over the counter"; the other two are sold to glass shops by their wholesalers, and are quite cost prohibitive. Without all three parts you can not do a proper installation.
Some parts stores sell a so called automotive grade of silicone. DO NOT believe it! Silicone contains acetone {fingernail polish remover also contains this chemical} which will eat into the paint allowing water to get to the metal, and rust will result. This is not opinion, this is fact, so trust your parts store at your own peril and don't ever claim you weren't warned.
Back glasses and Quarter glasses usually follow the same rules as windshields for installation. They are either bonded with Urethane, bolted in with butyl {1/4 inch}, or mounted to a latch and hinges for movable operation.
Door glasses can be glued, bolted, riveted, or snapped into place. Everywhere the D/G touches must be free of any glass or foreign objects. This especially includes the weather strip channel the glass rolls up into. Any piece of glass missed could shatter the new D/G resulting in double the expenditure and aggravation. Tempered glass is designed to shatter in such a way as to dull the individual pieces of glass, but can still result in glass splinters and puncture wounds, so the use of gloves is recommended.
There are various types of D/G regulators associated with the various kinds of installations, and a number of crossovers to boot. It is simply not possible to communicate every different kind, type, and probable problem that the "shade tree" will encounter in a book, let alone an article.
If you have reached this point and decided that this is better left to the professionals, there are a few more things you should be aware of. What follows is the most important part.
Everyone does the same work, so cheaper is better.This is a very common misperception, and has cost people more than can be calculated. A short-cut windshield installation is more likely to fail than a properly installed windshield. Consider that in an accident your seat belt and shoulder harness will lock you into an upright position, so if the windshield fails and the roof collapses, your neck WILL be crushed resulting in you or your loved one(s) becoming quadriplegics {unable to move below the neck}. Would you value the rest of your life at the $20 - $50 savings by having a "Johnny Pickup" do your glass rather than a qualified Glass Tech?
You get what you pay for.Not always, so when you have a windshield replaced I would recommend that you watch and make sure that they don't skip any steps. This article may be used as a reference. Most of the time you are better off doing business with a local "Mom and Pop" glass shop rather than a national chain because typically they take more interest in their customers/neighbors.
A good installer not only doesn't mind being watched, but will actually invite you to watch him/her do their job. Education is 80% of what they do, and the more you know the better protected you are and the more likely you are to be a repeat customer.
Auto glass replacement may look easy when done by a professional, but don't be fooled. Glass is dangerous, and can be deadly if it is not respected. Development of techniques, balance, and knowledge of systems is not something that can be imparted in an hour, day, week, or months. It takes a lifetime, and a true professional has dedicated his lifetime to your safety and protection.
