tjkj2002 wrote:
Yeah guess you haven't seen the printed materials for "proper" welding on GM,Ford,and Chrysler vehicles,all state you must disconnect the battery and turn the headlights on after the battery is disconnected to discharge any and all capacitors to prevent SRS deployment.It's not a myth,not that it happens all the time but it still happens.
Are you serious? "Proper" instructions from the same folks who tell you point blank to use "only" GM, Ford or Chrysler replacement parts on their vehicles? The same folks who say not to use a cellphone while pumping gas into their vehicle? What is the max fording depth which they tell you NOT to exceed for your vehicle? What is their position on replacing the OE bumpers with aftermarket, non NTSB approved bumpers? Are these "Proper" instructions coming from the same group of lawyers who authoritatively assure us that there is no problem with our torque converters, or that our suction based fuel supply system has no design flaws? FYI, headlights cannot EVER discharge the SRS capacitor. They are completely separate circuits with no physical or electrical link. The capacitor charge cannot flow backwards through the AECM or it would fry it. Trace the circuit and be edified.
tjkj2002 wrote:
Oh and I don't know what SRS systems you are working on but all the GENI and GENII systems I've worked on(SRS certified for both GM and Chrysler) there are only the SRS CPU,airbags themself,clockspring,wiring,and up to 6 impact/G force sensors.There is no arming sensor and the capacitor is part of the SRS CPU,which is only good for 2 accidents but the SRS light will remain on after the first accident(airbag deployment).
I too have been certified in SRS repair and replacement when working for the Herb Addcox Chevrolet Body Shop. Certification means very little. It indicates that you have have the ability to use a GM scan tool to identify what is causing the SRS module to set a trouble code, and either fix the connexion or replace whatever module is bad. Most Gen1 systems in American autos and all Gen2 contain the arming sensor and capacitor within the airbag ECM box itself. The description I gave earlier with 3 crash sensors was the basic elemental description of how a system works. Most modern systems with side impact bags can have 8 or more sensors but each directional cluster functions in the same way as previously described. Again there is
NO way to electrically trigger the mechanical shock sensors with stray voltage, It is absolutely, positively, definitely and without doubt, impossible. The ONLY path that juice can follow to get from the Capacitor to the accelerant is through these crash sensors. Some VERY basic info can be found here
http://www.auto-repair-help.com/automot ... air_bags.ptjkj2002 wrote:
the SRS CPU,which is only good for 2 accidents but the SRS light will remain on after the first accident(airbag deployment).
If you have been sending cars out the shop door with the SRS light on after a crash, you are endangering lives. The airbag WILL NOT deploy if the light is on. Contrary to what your GM, Chrysler, or Ford FSM will tell you(of course they tell you that it is a one time use item, they want to sell you a new one). the AECM unit can be reused indefinitely. I used to send them out to a company similar to this one...
http://www.myairbags.com/?gclid=COijuMn ... gwod-xUuEA until we got a hand held unit which would reset them in the vehicle.
But all of this strays from the initial topic. There is no such thing as stray voltage. Electricity is not a mystery, although there is a lot of superstition surrounding it. Electricity can only flow from point A to point B by the shortest path available, or the path of least resistance. The electronic components in a vehicle's computers are completely grounded and even isolated from the rest of the vehicle. If this were not the case you would fry the computer every time a 50000 volt static spark jumped from your fingertip to your door handle.
I'm not posting this info just for argument's sake or for my own ego. I just have a thing against misinformation, and do not think that superstitions should be propagated.