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Welding on the chassis of a computerized Porsche

Sometimes it becomes necessary to weld on the body or chassis of your Porsche. This would usually be part of a repair following an accident but could also be non accident related repairs or modifications that would require welding to be performed somewhere on the car.

We are specifically concerned about using the different types of electric arc welding. These include Stick, MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas) welding also known as Heliarc welding. All of these electric arc welding types use electrical energy (either A/C or D/C Voltage) to generate extreme heat at the localized spot where the weld is taking place. As part of the welding process, an earth connection (welder ground) is made near the welding site to isolate and collect this energy during the welding process; however, not all of the electrical energy will necessarily take this path. High frequency electrical energy can be introduced into the car’s grounding and wiring systems through the uni-body type chassis which is the common grounding point for most of the vehicle’s electrical devices. The electronic control units (computers) in the car are at risk and can be damaged by this stray electrical energy thus potentially creating a serious and expensive problem for computer controlled Porsche models.

If you are going to weld on the chassis of any computerized automobile, it is preferable that you disconnect and remove all the controllers, even though this may not seem realistic. The Airbag controller should be removed as this is probably the most volatile controller. Most Airbag control units are located in the center console; however you should confirm this for your specific model. Take out the DME (Digital Motor Electronics), Immobilizer, Alarm, Climate Control and other controllers including the Radio from the dash; this is a very sensitive component. The ABS (Anti-Lock Brake) system controller should be removed from the front trunk; this is also a critical controller.

Do not just disconnect them; remove them from the car completely because many controllers have multiple ground connections and thus more opportunities to catch stray voltage. Additionally, relative to the battery, leave the battery terminals connected however install an automobile battery surge protection device on the batteries terminals, this will help limit voltage and high frequency spikes.

Relative to the area being welded, some fundamental precautions can go a long way toward insuring a quality weld and the health of the automobile’s electronics. Clean the surface contact areas of all pieces being welded, all the way down to bare metal to insure the best connection. Also, clean the area down to bare metal where the welder’s ground clamp will be positioned. Place the welder’s ground connection on or as close to the welding area as possible; the use of multiple ground points around the welding area is suggested and encouraged.

Utilizing a professional welding business is recommended because they should have the correct tools, the knowledge and experience in setting up the equipment and preparing the surfaces for welding. In doing so, the professional will minimize the length of time needed for the actual welding process to take place minimizing the exposure to the welding process. Further recommended is the use of MIG welding on the automobile chassis in place of TIG welding. This is due to the extremely high frequencies generated to start the TIG welding process and therefore the increased possibility of damaging sensitive electronic components.

Tony Callas
Tom Prine

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