What happens if you ohm test an AIRBAG?
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- Опубликовано: 6 июл 2024
- Steve shows you airbag circuit safety, then crosses the line to see what happens if you break all the rules.
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If airbags were that sensitive, they would blow from static electricity. I have ohm tested airbags for years with no issues. It may not be safe. But I haven't had anything happen yet.
True story! Plus, if you scan the SRS module, there is a resistance data pid. That resistance measurement is always active, you’ll get an airbag light if that pid goes out of spec.
Very good info. It took a lot of searching on airbag safety and deployment requirements before I stumbled on to this upload. Thanks.
I’m glad you found it helpful.
Thanks for the lesson on the little shorting bar, solved my 0 ohms problem!
Awesome! Glad it was helpful.
I worked with electric detonators as a shotfirers assistant. The blaster included a moving-coil ohm-meter that was putting about 10 mA through the wires. It takes a lot more than that to fire the detonator.
Thank you, an expert in the industry. Sometimes lawyers make too many warning stickers.
AWESOME. Thank you very much for sharing. From France.
Thanks. Bon jour!
whoa ...you are much braver than i, thanks for the detailed education Steve ! (lol 12oz, funny blooper ! :)
Yeah, you can tell what I was thinking. Haha.
very clear explanation
Thanks. Cheers!
Thank you for this. Saves me from doing this. Now I have a slightly different problem, how do you know which side of the two pins was 12V and which side was GND? The problem is my 2-pin airbag connector can be inserted either way.
To answer your question, the wiring diagram from service information will tell you which is +12v. I haven’t come across a connector that works either way, but the inflator will deploy no matter which direction the current flows.
@Tool Demos Congratulations on this content, is very good, I apologize for interfering here but I have the same doubt, then if you invert the wires in the airbag bag connection he is not at risk of bursting? In case someone wants to install some accents of a different brand of car from the brand of your car knowing which are the two wires of the airbag bag there is no positive and negative to connect? no polarization? Parabéns por este conteúdo, é muito bom, peço desculpa por interferir aqui mas tenho a mesma duvida, então se inverter os fios na conexão da bolsa de airbag ele não corre o risco de rebentar? No caso de alguém querer instalar uns acentos de uma marca de carro diferente da marca do seu carro sabendo quais são os dois fios da bolsa do airbag não existe positivo e negativo para conectar? não tem polarização?
To better explain my doubt.... Example, install some Subaru seats in a VW Golf and connect the Airbag from the seat, just connect the two wires of the Airbag without worrying which is the positive or negative?
I really enjoyed your video thank you. I'm not sure if you will see this message but I wanted to mention something about the current draw. 6A I believe is much too high to consider when its in the car and I think it was more so your car batter providing a constant voltage @ 12V causing the current to max out at 6A. The driver IC's inside the srs modules typically push 1-3A's for each output. The one I was just working on used a TLE8718 for example if you wanted to pull up the datasheet. Made me wonder if the value you were reading is a diagnostic resistor in parallel with the squib igniter coil e.g. (4ohm squib + 5ohm diag resistor which would read at 2.2ohm but then you could get a current of 1.25A @ 5V which seems more in line with the tle8718 high side switch. Or maybe its just the single squib that reads at 2ohms but still it uses a constant current from the driver chip maxed out around 2A. This would still bring the voltage down to around 5V and may could provide sufficient heat through the squib to ignite it. Still pretty high for any DMM but much lower then the 6A. Just something to think about. Most dmm's work around 1ma when testing.
Food for thought, thanks. Honestly, I’d like to do some more testing out of curiosity.
Does your meter have a diode voltage drop function?
Yes it does.
Hi my friend. Educational video for sure. Is it the same principle you may use to discover the appropiate diode (in ohms) so that you can cheat the SRS in thinking there is an airbag? Thinking it when you have a track car and you take out all the airbags and you dont want error lights in the dashboard.
Hi Red Zone. Exactly, the SRS module continuously monitors that resistance PID and will set a code immediately if it changes, even slightly.
@@ToolDemos so… the proper way to determine the exact ohms diode would be to just do the test you have done right? I mean, connecting a multimeter to an airbag and test its ohms capacity? In your case, if it is 2.1ohms, could you buy a 2.1 diode and wire the car harness and make it think there is an airbag?
@@redzone5655 yup, that’s it Red Zone. If you have trouble, double check your connections (solder or butt connectors) they could cause resistance. If you have a scan tool, look at live data in the SRS module, it should give you the resistance reading for the airbag (squib circuit).
That was fun!
I thought so too!
Interesting!
How do i find out how many ohms my airbag hold so i can by pass it with a resistor?
They’re all pretty universal. If you search airbag bypass resistor, you’ll find a bunch of them.
Note: it is not safe to operate your vehicle with the bypass, it’s for diagnostic use only.
How would you find out the minimum voltage to deploy an airbag? I know that it probably varies with manufacturer, type of inflator, and manufacture date, but I would still like to find out or at least have some idea. I have set them off consistently with a 9 volt battery. Could it be possible to set them off with the output from a cellphone or tablet battery?
My guess is that a cell/tablet wouldn’t pop an airbag because they typically run on less than 4V. To find out, the only thing I can think of is using a variable voltage power supply. I’d attach it to the inflator then supply low voltage, slowly increasing it until the bag deploys. If you try that, let us know what you find out, I’m curious now.
@@ToolDemos hook a usb cable to a portable battery charger. Cut the cord and hook up positive and negative
@@ToolDemos Air bags can be set off with static electricity, that's why is shorting bar in place, I'm sure of that, so any battery or cell will do the job as good. I was expecting you would hook up in circuit potentiometer and slowly increasing voltage whole measuring current and voltage.
@@bahn5ee that’s a good idea.
At 12v or 14.4 volts with alternator running, the airbag will deploy in 100 milliseconds. It is meant to deploy super-fast in a collision of course. But it is entirely likely that a much lower voltage will set it off, only more slowly. It might take a few seconds for the igniter to heat up sufficiently at say 4v. 4v / 2 Ohms is already 2A. That still a lot of current for a little igniter unit to dissipate. It's going to get hot.
Meh, ...what I would have done is gradually ramp up the VOLTAGE being sent to the airbag until it blew. Then you'd know both the current and the voltage required to set it off.
Just dividing the 12.5v (or 14.5v with alternator running) voltage of the battery by the resistance doesn't tell you much. It tells you the maximum current that might be used in practice to set off an airbag in a collision, but not the minimum current required. For all you know an airbag might go off at 6v, or at 4v, but might take 2 seconds to heat up sufficiently to blow rather than 1/10 of a second.
Next time, yes I’ll do that.
Put it on diode test and see.
Good idea
Good test though
Thanks
The multimeter puts about .600 volts out when using the resistance measurement
Not nearly enough to ignite the squib .
One of the tests the module does is a resistance test in similar fashion to what a DMM does.
Just sayin
Exactly right.
Not true. A normal multimeter will put out about 3,3v on the diode testing mode. High end ones like some flukes and probably the snap-on he used put out 5v. You can easily check using 2 multimeters: put one in diode test mode and the other one in voltage mode.