Pressure Sensors And Paintless Dent Repair
History of Automotive Sensors
[Update: I Do Retract My Original Version Of This: My research is based upon a very limited understanding of the Authors that I have read. Im certain that my assessment that side impacts do not save lives, is not entirely true. In fact, I am drawing those conclusions from only 7 papers. Again, Im certain that I missed much, but my goal is to keep people alive. If it helps even .00001% of the population, it is worth it 100%. I apologize for that comment.] Paul WhitehornThe first patent for an airbag system in the U.S. was issued to J.W. Hetrick on August 18, 1953. It wasn’t until 1970 when the National Highway Traffic Safety Administration tried to make laws surrounding restraints and airbags. There were several messy court battles spanning almost two decades with the Nixon and Regan administration, which prevented airbag safety laws. It wasn’t until 1995 that congress finally passed a bill requiring airbags.
The very first side-impact pressure sensor was Volvo’s 1995 850 model. BMW was the first to design an Inflatable Head Protection Systems (HPS) system in 1998, which is still standard in all 5 and 7 series. Today, these sensors are largely only found in higher-end German manufactured vehicles, like E and S Class Mercedes, but they are also found in many Chrysler vehicles manufactured in Germany. According to a leading expert, on side collision pressure sensors, Adrian Hobbs, paraphrased: “It has also been proven that they are largely useless and don’t save lives, its a sales tool to make passengers feel safer than they are.” In his paper “Dispelling the Misconceptions About Side Impact Protection”, in SAE Paper No. 950879. Its largely due to the nature of these types of impacts. The amount of force required to deploy the airbags, goes hand in hand with the metal being ripped, releasing the pressure. Also, the survivability of impacts at this speed are rare and often not attributed to a small cushion.
Why It Is Important For PDR To Understand
The vast majority of automotive sensors for accidents are dedicated to frontal collisions. This is the most common kind of crash a vehicle is likely to encounter. However, as it relates to paintless dent repair, the newer side impact sensors are the most relevant. Since, if a PDR technician doesn’t understand some of these sensors it can increase the time or prevent side airbag deployment entirely.
Understanding automotive sensors and how they relate to paintless dent repair can mean the difference between major injury and a minor injury, in the event of a collision. Admittedly many of the features that today's vehicles have are redundancies which only help in very specific situations, regardless if you need them and they fail, it could be because corners were cut in a paintless dent repair. However, this isn’t about past failures. Its what you need to know as a consumer or technician to ensure that the vehicle will be safe when dealing with a side impact.
Identifying These Rare Chambers
The tale-tale signs of a panel with this feature is by looking at the interior panel. Once the doors interior panel is off you will see a blocked out cavity or metal plate, instead of the typical breakaway fabric with the black sealant. In all vehicles except the Chrysler, it is pop-riveted in. This cavity is pressurized and if you drill a hole into it, you can prevent it from deploying side airbags, in the event of an accident. You do not need to be concerned if you are doing a repair through the window.
Avoid Drilling Into Pressure Chambers
Unlike front end collisions that have significantly more time to respond to the crash, side-impact response time must happen much faster, since the crushable space between the damage from the outside and the occupant is much smaller. The reaction time for the sensors must be within 3-5 milliseconds and deployment of airbags must be 7-15 milliseconds. Although these airbags have had virtually no improvement for occupant safety or survivability, for T-collisions and the panel at 30mph usually ruptures on impact, to begin with, it is still important that we leave these vehicles the way that we found them.
Pop Rivets The Right Work Around
Invest in a nematic pop rivet gun and drill the rivets out and simply replace them and the seal. It should also be noted that the battery needs to be disengaged from the sensor for one hour before messing with it. There have been cases where the airbags deployed just from drilling into the pressure cavity and removing the rivets. Charge accordingly. To do these panels correctly, you should be charging triple your normal rates at a minimum. I currently charge 300$ for the entire process, not including the dent repair itself.
If You Must Drill Keep Atmospheric Pressure
The cavity itself is not affected on the front side of the panel. That is, anything in front of the glass is not within the chamber and if you must drill this is where it should happen. Furthermore, if you must drill into the chamber make sure that you do not use a typical plug. That plug will do nothing for the pressure in that chamber, even if it had cavity wax or glue. Silicone X-Tream Tape, is a permanent leak sealant, that will keep the chamber at a safe pressure if struck. It will maintain the pressure change threshold of 34mb or about 3-4% atmospheric pressure. It may not look as pretty, but it will get the job done.
Conclusion
Even though side-impact pressure chambers are still in their infancy and they don’t save lives for most collisions, we should practice maintaining the proper pressure, within the chamber. Many automotive manufactures will continue to use them as a selling feature for their vehicles. Know and understand these sensors, how to identify them, and how to pop rivet them on and off.