Design: Failures Occur Despite Safeguards

Numerous electrical ignition sources for automotive fires are available, despite efforts made in design to avoid them. Such ignition sources exist in properly maintained vehicles in normal operation, as well as in vehicles compromised by damage, age, wear, modification, or collision.

Electrically protected circuits can still have ignition potential. For instance, if a stranded wire is abraded such that only one strand remains, even if it is operating at rated current, the damaged wire may heat to the point of igniting nearby combustibles, or it may burn through and cause a parting arc. Localized heating of conductors from grounding, shorting, or poor or intermittent connections can cause sufficient heat for ignition while staying below the current level necessary to open the fuse. In rare circumstances, normal arcing within an electric motor (e.g. fan motor, electric pump, wiper motor) can cause ignition of flammable vapors.

Some high current electrical cabling has no circuit protection by design (starter, alternator, positive cable from battery). If a short to ground occurs, arcing and sparking is likely to occur.

Loose connections can be the source of high-resistance heating. For more information, click here.