Tech Tip: Getting That Last Air Bubble in a Repair

I recently trained a technician that had years of experience, but wasn’t completely pleased with the quality of his repairs. He knew all the tricks in the book. He knew how to flex those pesky stars with a probe. He knew how to apply heat and pressure from the inside of the vehicle on difficult combination breaks. He even knew how to drill and pop a mini bull’s-eye to fill a stubborn leg. What he didn’t know was that the reason he had to resort to all of those tricks was because he didn’t set the bridge properly to begin with, which is the most important trick of all.

You can eliminate time wasted in flexing, drilling, and manipulating a break if you set the bridge and injector properly. The objective is to create a good seal without applying excessive pressure to the break. Most technicians who experience problems filling a break have over tightened the injector. To avoid this make sure not to turn your injector more than ½ of a turn once it touches the glass. The correct amount of tightening of the leveling screws will vary depending on the curvature of the glass, but a good starting point is two complete turns after they have touched the glass.

If the bridge is over tightened the injector will exert enough pressure to close up a leg on a star break or compress the surface of a bull’s-eye. Before you reach for your drill or probe to try to fix the problem, first make sure your injector isn’t too tight. Try to spin the injector. If there is a lot of resistance, it may be too tight. Just loosen the injector by rotating it one quarter turn counter clockwise. You will be surprised at just how often this will solve your problem without having to flex the glass and risking further damage to your customer’s windshield.

Do you ever have trouble with the dreaded black dots or crescents of air left in your repairs? You would swear that you had all the air out, but after you take your injector off and cure, the bubbles are back. The most common reason for this is again, too much head pressure. The break is flexed inward due to the pressure, so when the injector is removed it snaps back, ever so slightly, to its original state. This creates small areas within the break that are not completely filled.

One big reason people tend to over tighten their injector is that they wait too long to change their end seal. A broken down end seal will often require much more head pressure to seal correctly, so to make sure it doesn’t leak, technicians just add more pressure. That will stop the leak, but your repairs may suffer. Don’t try to get 30 or 40 repairs per seal. It just isn’t worth the extra couple of cents per repair to fight with a sloppy end seal.

So, make sure you go back to the basics and create a solid foundation for your repairs. You may find that some of those breaks that used to give you lots of trouble aren’t so bad after all.

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