More 'Touching the Cables' Stories

[rmoore]

Received the following message from a Captain with a southern US city fire department. What is disturbing is that this same subject comes up time and time again yet no automaker will verify if it is bogus or a good thing to do.

"Chief Moore, During a recent visit to local car dealers to check out some of the latest supplemental restraint systems, two dealers advised us to disconnect the neg. cable then the pos. cable and hold them together. They advised this would deplete any capacitor charge build up. Ever heard of this?"

My Reply:

I've heard of doing this but at the same time, have been told that it doesn't work as far as rendering the actual airbags safe to be around. If touching the cables did work, I wonder why we haven't been told about it long before now. Currently, no automaker instructs responders to do this in any of their advisory bulletins.

Even if it did work, the actual airbags would still remain vulnerable to deployment due to static electric charge, short circuit, etc.

As for me, I'm not going to recommend it.

[Rescue101]

A thought to ponder.Ever notice when blasting crews are setting charges they ALWAYS leave the squib wires twisted together until they are ready to make their way out of the area?Now since an air bag inflator is nothing more than a modified squib,and since we generally can't reach the wires to tie them together,why not connect the main positive and negative leads together AWAY from the battery.In other words take both leads off the battery and hook them together.While I'm confident it won't remove all danger of working around the bags it's just another step at securing the system.It will hurt NOTHING.The only way I know of to remove any air bag threat is to remove the airbag,again not practical in emergency ops.T.C.

[cardoc]

Hello folks. I work in the automotive industry and we have done this in the past to disipate voltage in older cars electronic modules. Unfortunatly this as I have been told does not work on newer cars much lessd the new technology of the air bag DERM module. It was built to hold power in it to deploy the airbags even if the battery or power supply to the derm was diconnected. The components are called capasitors which you all know. I have a further question to ask as well. I have been searching archives and most of you do cut the battery cables. Is there something to this that I have missed. With the newer cars comming out with power seats, power foot pedals, power roofs now on the GM Trail Blazer, would we cutting the cables then disable our ability to electrically move this objects if needed. Understanding how to deal with airbags and systems I feel is the key. What are your thoughts on these subjects. Thanks in advance. Alan

[Bones42]

cardoc, I can push the power seats and power pedals with my extrication tools. I feel far safer having the power disconnected than the convenience of using the power seats. Not saying it is not a consideration, but each situation will dictate what options you use.

Also, aren't some newer cars coming with the feature that after an accident, all the power seats and such will automatically retract back to their furthers points?

[JorgHeck]

Hello!

I feel far safer having the power disconnected than the convenience of using the power seats.

I don't agree with this. Using the electrical power of the vehicle if possible could save much time! And I don't see a big risk if you do so when you follow the airbag-safety-rules and when you have a charged hoseline in service. I know that is's easy to move or remove the seat of a modern vehicle because its a very complex construction. You also could save a lot of time when you could lower the windows elektricaly.

Also, aren't some newer cars coming with the feature that after an accident, all the power seats and such will automatically retract back to their furthers points?

I don't know any car where the seats are move after the crash. But there is the possiblity to move the seat and the steering wheel after you take the key from the ignition.

There is also a new in-crash-device from mercedes-benz which is called "PreSafe", this device moves the seat in an upright position, the windows were closed and the seatbelt gets some tension when the vehicle detects a critical situation.

[firenresq77]

Check to see if the seats need moved before you cut the cables. Windows......... don't worry about rolling them down first. Once you start prying on doors, they're going to break inside the door anyhow. The cables still need to be cut........

[nmfire]

This trick may work on some electronic devices but I'll be damed if I'd trust it on a newer automobile. The electroninc systems in today's cars are incredible. Touching those cables together won't do squat to disarm anything.

[Rescue101]

NM,And you're baseing this commentary on the basis of which document or repair manual?I look at "new car"schematics everyday as my livelyhood and I'd be hard pressed to make a sweeping statement such as this.The only way you could design a control module so that hooking the cables together WOULDN"T WORK is thru a diode pack.Go study the major SRS control modules schematics and SHOW ME THESE DIODES!Good luck.Now will the cables hooked together remove all power from the capacitors?Maybe yes maybe no depending on model.One thing for certain;it MAY work and will HURT NOTHING.The ONLY way to make an airbag "safe"is to TOTALLY remove it from the vehicle.PERIOD! T.C.

[nmfire]

Well then tell me I am wrong if you read these schematics all day long. Based on your schematics, would you place yourself in front of an undeployed airbag after touching the cables together?? Probably not and neither would I. Thats the point I am making, it is not a reliable, approved, or proven method to accomplish much of anything.

[JorgHeck]

As Ron Moore says:
No car manufacture instructs responders to touch the cables, and I'm sure they would do if it could help! It would not change anything for the rescuer if you do it, so why?

I also think it could be dangerous to put the cables together, when their are two batteries in the car and you are not aware of this fact. Rescue101, what do you thin could happen when you put together the cables of the first batterie with the second batterie still conntected?

[Rescue101]

Hehe Jorg,usually a BIG spark!The number of vehicles that utilize two batteries are not that numerous.Most diesels,some hybrids and a FEW conventional vehicles have them.As with anything else in vehicle rescue NOTHING IS CARVED IN STONE.I often make the mistake of assuming there is still a bit of common sense left in the world when everyday realities indicate otherwise.This is one can of worms I'm REAL sorry I opened;You guys do whatever you want but the only safe airbag is a non-existant or removed from vehicle variety.Thousands of people worldwide will find a way to kill themselves so I've got to question the insanity of those who try to prevent it.Perhaps Darwin was right.T.C.

[Fire304]

Originally posted by Rescue101
The number of vehicles that utilize two batteries are not that numerous.

Add this one to your list, cars with big thumping stereo systems. Audiophiles often add a 2nd battery to power their systems, especially those who enter their cars in sound competitions. Since they get penalty points for visible modification this 2nd battery is often hidden from view. I saw a Honda Civic with 3 extra batteries hidden in under the hatch back with the amps which were under the boxes that the subwoofers were in. The sound system batteries are usually run through a diode to protect the car's starting battery but not always. There are also often very large capaciters hidden in the systems which will give you a big spark too.

[Rescue101]

Or some major league deafness.Did I mention my regret at opening this can of worms?Maybe disconnection is a bad idea also?How many vehicles has anyone here seen ignite AFTER the arrival of responding personnel?I can't immediately think of any but I don't log a lot of this stuff so I may have overlooked something.T.C.