Airbag Switches for Law Enforcement

The following points are intended to help explain and elaborate on the specifications. 

Multistage airbag switches

Multistage airbags, as used in many cars built after 2001 including Crown Victorias and Impalas, require multistage airbag switches in order to simultaneously turn both of the airbag’s stages (detonating circuits) on or off.

The idea of the removable key is a federal requirement and insures that only the person possessing the key controls the switch.

 Yellow Light

NHTSA only requires only one light (yellow) to indicate when the airbag is turned Off.

More than one light can be confusing, especially to anyone who is color-blind.  If there is more than one light, it becomes a matter of telling colors apart. This is especially difficult for most color-blind people when the lights are green and yellow, and is even more difficult in the dark

If there is only one indicator light on the switch, it indicates conclusively that the airbag is OFF, even in the dark and even if the operator is color-blind. (When the airbag is on, there is no light on the switch.) Therefore one light on the switch is far better and less confusing than two lights. 

   
Internal Fuses

Unlike Airbag Switches by Sensible Solutions, some switches contain an internal fuse. The purpose of the fuse is to provide evidence of a switch’s position when a detonation impulse is received from the vehicle’s airbag controller. The idea is to protect the manufacturer from liability in case someone claims the airbag switch was turned off but the airbag deployed. There are two problems with this.

Having a fuse will force the owner to replace switches periodically. For this reason, the spec requires the manufacturer or provider to replace switches with opened fuses at no cost to the owner for a period of ten years. (Alternatively, the spec could state that there shall be no internal fuses). Sensible Solutions can provide switches with an optional external fuse if this is requested, but once this issue is understood, the added fuse has never yet been requested.

Gold Contacts  

 This is an important advantage because gold doesn't corrode, and the switches will last far longer than non-gold contacts. Other metals are used in switches when the current is high enough to insure that the contacts clean themselves when the switch is moved from one position to another. Usually this contact cleaning requires at least 25 Milliamps in the switched circuit. But in an airbag circuit, the current is well below 3 milliAmps, so corrosion of the internal switch contacts is inevitable. This is well known to engineers in the electronics industry, and is why they use gold contacts in low current applications. In the Auto industry, gold contacts have been required on low current electronic circuits since WW2. 

An airbag switch that doesn't use gold contacts will eventually fail because the buildup of internal corrosion on the internal contacts will add too much resistance into the airbag circuit. The only remedy then is to replace the airbag switch.

The auto industry uses the SAE (Society of Automotive Engineers) specifications for in vehicle systems that transmit data which also require gold contacts on electronic connectors. These are covered under SAE AS 39029 and SAE/UCAR-2-4 Rev3. Sensible Solutions airbag switches use gold contacts.