Vehicles contain an array of restraint system innovations designed to keep occupants safe during some type of collision. So why is it that few collision repair personnel are knowledgeable enough to safely diagnose or repair them?
If you mentioned restraint systems while talking to your next door neighbor after work one day, he or she might look at you a little cross-eyed, step back a bit and begin to conjure all sorts of ideas about your choice of "hobbies."
If your neighbor happens to be involved in the automotive collision repair industry, however, you would probably be able to talk for hours about the trials and tribulations you have each encountered while trying to estimate, repair or replace these highly sophisticated systems after a collision loss.Today's modern vehicle operates with several systems that fall under the "restraint systems" heading. These being: airbags (including knee bolster type, side curtain, side seat back and passenger), lap and shoulder belts, seatbelt pretensioners, seatbelt sensors, child safety seat anchors and whiplash safety seat mechanisms. Many of today's vehicles employ all of these innovations, in an effort to maintain priority one – the safety of the vehicle occupants during some type of collision.
Generally, everyone that drives a car is aware of these devices, but few collision repair personnel are knowledgeable enough to safely diagnose or repair them. Part of the reason for this is that carmakers are very innovative, constantly adding, tweaking and improving these "mysterious" systems to enhance driver and passenger protection. These constant improvements make it difficult to stay in tune with these evolving systems.
Basic restraint system operation
It is highly likely the vehicle you are driving is equipped with seatbelts and certain components of a Supplemental Restraint System (SRS) – airbags (some will be equipped with advanced frontal airbags), seatbelt pretensioners, seatbelt buckle sensors and seat sensors that monitor seat position and occupant weight (occupant classification systems). A vehicle's on-board computer constantly monitors the functions of these systems while a vehicle is in operation.
In the event of a collision, the system will already recognize the weight of the passengers in the seats, if any and how far away they are located from the airbag module. (The seat may have sensors in the track that monitor seat position.) This knowledge will determine the rate at which an airbag will deploy should it be necessary. This safety feature is particularly significant when smaller occupants are in a vehicle – children or smaller adults who may have been injured by older less "smart" airbag systems. Once triggered, the airbags will deploy and seatbelt pretensioners will activate, pulling an occupant down into the seat, in a safe position to absorb the airbag impact. The seats themselves, if equipped with whiplash protection devices, may flex at the hinge joints, allowing greater movement than normal, to protect from whiplash. All of this happens in fractions of a second.There are a series of sensors located in strategic areas of vehicles that control the deployment of these devices in the event of a collision. Typically the sensors are electrical switches that activate when the forces exerted in a collision are great enough to close the open electrical circuits they are located in. Once closed, the SRS components deploy.
The typical propellant for inflation, when airbags were first developed, was a compound called sodium azide. When connected to live electrical sources (such as an igniter in the system) sodium azide burns rapidly and forms nitrogen gas that inflates the airbag. Unfortunately, when sodium azide burns, it creates heat. Heat has the potential to cause fires in plastic trim and other flammable areas of an automobile.
Most modern airbags are inflated by containers of compressed gas. These operate in a similar manner to sodium azide, but utilize much less space and are much safer with regard to heat and potential fires. Most cylinders look like a pipe full of holes, with a wire on the top. The wire is connected to the airbag control module. When the disk inside the cylinder receives a signal from the control module to ignite, it does so and gas escapes from the holes in the pipe and inflates the airbag. Obviously, this is a very simplistic analysis of the system, but it's important, before delving in deeper, to understand the rudimentary operation of the system.
The tough stuff
The difficulty regarding Supplemental Restraint Systems in the collision industry involves two areas:
1. Estimating the damage that involves deployed SRS components.
2. Repairing Supplemental Restraint Systems.
Estimating damage involving SRS
When you begin to analyze the damage to a vehicle with a deployed SRS component, you will need to look at several key sources of data, to determine what should be replaced as part of the repairs. Initially, you will need to determine what class of SRS the vehicle is equipped with.
The good source of information that is readily available is the estimating database you are using. Most systems have information regarding which components should be replaced or tested in the event of a collision. Each platform is a little different, but they will usually get you through the basics of necessary replacement components. However, this information is only a guide and should be utilized to point you in the right direction.If you are uncertain where to find this information in your respective system, contact the help department of the particular vendor you are using — they all have one. They will walk you through the details.
Often, a quick call to a dealer, utilizing the VIN, will get you some specifics with regard to the particular system employed in the vehicle. Most parts and service departments will give you this basic information.
Usually, when looking at a vehicle with deployed airbags or SRS components, it is fairly severely damaged and probably not drivable. After your initial inspection and determination of what systems are on board, speak with the vehicle owner and ask them some specifics about the loss:
- Which seats were occupied in the loss and by whom?
- How fast was the vehicle traveling at impact?
- Were seatbelts in use during the impact?
The answers to these simple questions will help guide you to a decision on how to handle the appraisal on the vehicle in question. Knowing if someone was in a seat during a loss, and how heavy or tall they are, will help determine if items not normally visible (such as seatbelts and pretensioners) were damaged in the loss. Additionally, there are airbag systems that deploy only partially in a loss, depending on impact severity.
Obviously, dealer service manuals or mechanical manuals produced by vehicle manufacturers are the best, most accurate sources of information. Since manufacturer service information is available through OEM repair information Web sites, it is easier to obtain information on current model years than it used to be. Sometimes, however, complete information on newer models is difficult to get through these sites. Many times, the dealer from whom you purchase your parts will allow you to utilize their service manuals for diagnosis.There also are good mechanical estimating programs being used in the marketplace today. You may have access to these systems through a local mechanical shop, such as one to which you sublet alignments. These programs are usually current and utilize information directly from vehicle manufacturers that can help you diagnose SRS damage. They typically explain the diagnosis through symptom checks and manufacturer recommended procedures — all of which can be printed and added to your file for estimate "back-up."
Every system works similarly, but differs in detail. The Inter-Industry Conference On Auto Collision Repair (I-CAR), the Automotive Technical Education Group (ATEG) and other training groups will provide the basics of these systems, so you will understand the details when you get them from your dealer source. Do not attempt to muddle your way through an SRS diagnosis. Research it well and document your research information when compiling your estimate.
Repairing Supplemental Restraint Systems
Most SRS components, once deployed, are not repairable. That is true in most cases, except for wiring damage. Even though it is generally believed that airbag wiring must be replaced if damaged, the fact is, some manufacturers recommend repairs for certain kinds of damage and offer detailed instructions on proper repair procedures. Care must be taken when repairing wiring however, so that resistance is not changed, altering the signals to the SRS and causing improper deployment/operation. Always defer to the vehicle manufacturer's recommendations when splicing or repairing wiring, sockets or pigtails.Most collision facilities can safely replace damaged components and have a qualified dealer or specialty repair shop, test the system once the components are replaced. Nearly every system today utilizes some form of "self diagnosis." Basically, the vehicle's computer system monitors electrical values that are pre-stored references and compares them to existing resistance values, amperage and voltage to determine if a fault exists. Many times, once all of the damaged SRS components are replaced and the vehicle power is re-introduced, the system will diagnose any faults and, if none are found, "clear" itself.
Although very technically sophisticated, these systems are easily repaired if your technicians have had some basic training, understand the systems, have the proper access to technical information and the proper tools. Make certain nothing is left to chance when performing these types of repairs and follow all of the manufacturer's recommended procedures to the letter. A little knowledge can be dangerous and have devastating ramifications if repairs are improperly completed.Even handling of airbag components can be dangerous, as static electricity can deploy an undeployed airbag under the right conditions. Always carry undeployed or partially deployed airbags facing away from your body for this reason. Carry side curtain bags, facing the ground, away from your body and anyone else who may be in the vicinity.
Fully understanding SRS operations takes lots of training. The average estimator or technician in most shops does not have enough training to fully comprehend every system function on today's vehicles. Since lives and safety are at risk when working with these systems, make certain the repair of these systems is entrusted to a knowledgeable partner if you have any doubt with regard to your ability to safely repair them. Remember, don't fear them – respect them.Education will become your most useful tool in making these types of repairs. Know what you are doing before you undertake these types of repairs. Everyone involved will benefit if you do.
