air bag light

[tiredmec]

I changed out the half doors. The replacement door has a extra plug so 6 wires. Now the air bag lamp is flashing Any idea what plug goes too. Can I jump it. It may be tough to get belt retractor out of old door. Or can it be reprogramed in Forscan. Need to change inside panel as wrong color. Wasn't going to bother but may have to.

 

[Curious Hound]

I'll try to check for a diagram this evening and see what I can figure out. My guess is that, tjere was a crash detector in the door and maybe an airbag. If so, jumping them out may require a resistor or something to tell the system that there is a device there instead of a jumper wire or something missing.

 

[RobWigglezz]

There is a self test for the restraint and air bag system so forscan might have the option. I think the number of times the air bag light flashes is also a code.

This isn't the answer, but it talks about the flashes

Air Bag Control Module: Description and Operation — 2001 Ford Ranger 2WD V6-4.0L VIN E Service Manual ~ LEMON Manuals

Repair manual for the 2001 Ford Ranger 2WD V6-4.0L VIN E, including electrical diagrams, bolt torques, and labor times.

lemon-manuals.la

 

[Curious Hound]

Here are 2 of the restraint system wiring diagrams for a 2009 Flex. I looked at the drawings for my 96 Explorer and they were more vague. But, as I suspected, this shows a resistor in the crash sensors. Without that, you will definitely have a fault. Unfortunately, it doesn't say what value the resistor is. Each airbag module also has a specific resistance as part of its igniter.

If you start messing with this system, make sure the battery is disconnected. Shorting the wrong wires together will deploy airbags and you could get hurt.

 

[pentode]

Is there a link here I'm missing? I'm not seeing the schematic.

Edit: I'm most definitely not an airbag guy so I'll need someone to double check my work on this but I do know how to make computers happy so I have an idea of how to approach this. Just don't want to elaborate until I see the schematic or get a wingman.

Edit2: I just want to make absolutely sure nothing I suggest causes someone to set off an airbag. I was going to suggest picking a very safe high value resistor (10k) and go down in increments from there. However, a quick search reveals plausible data on a mustang forum that suggests that the mustang airbag resistor is 2.3 ohms. This is totally reasonable to me, some kind of coil possibly, but that's not where I'd start unless I had more info. Learning about airbags has been on my list for a while now. Checked off the "how much gas is in the hose?" question earlier so I'm primed to learn.

 

[Curious Hound]

Is there a link here I'm missing? I'm not seeing the schematic.

Edit: I'm most definitely not an airbag guy so I'll need someone to double check my work on this but I do know how to make computers happy so I have an idea of how to approach this. Just don't want to elaborate until I see the schematic or get a wingman.

Edit2: I just want to make absolutely sure nothing I suggest causes someone to set off an airbag. I was going to suggest picking a very safe high value resistor (10k) and go down in increments from there. However, a quick search reveals plausible data on a mustang forum that suggests that the mustang airbag resistor is 2.3 ohms. This is totally reasonable to me, some kind of coil possibly, but that's not where I'd start unless I had more info. Learning about airbags has been on my list for a while now. Checked off the "how much gas is in the hose?" question earlier so I'm primed to learn.

Yeah. I did the typing and forgot the photos. They're there now.

 

[pentode]

Presumably that switch is what sets off the airbag?

And the resistor provides a sensible reference that isn't either open or short?

I need to stop putting off learning about explosives.

 

[Curious Hound]

Presumably that switch is what sets off the airbag?

And the resistor provides a sensible reference that isn't either open or short?

I need to stop putting off learning about explosives.

Yes. In the sensor, the resistor tells the computer "I'm here and functioning." The switch contacts say "deploy the bags!".

In the airbags them selves, the resistance is something like nichrome wire (or could be nichrome wire) which heats up quickly and ignites the charge. But the microcomputer is probably also looking for that resistance to know that the airbag device is in the circuit.

 

[pentode]

I have more info and understand the electronics part now...

Yes. In the sensor, the resistor tells the computer "I'm here and functioning." The switch contacts say "deploy the bags!".

In the airbags them selves, the resistance is something like nichrome wire (or could be nichrome wire) which heats up quickly and ignites the charge. But the microcomputer is probably also looking for that resistance to know that the airbag device is in the circuit.

This came in as I was typing. So now I'm just trying to understand the repair. Are we talking about rear half doors on an extra cab? Just wondering why the harness would care about a door with extra features that it didn't know about...

But either way, I do feel like 2.3 ohms sounds like a sensible value for such a circuit. I'll just quote what I found in another forum:

"The squib that detonates the air bag has a resistance of 2.3Ω if it is intact and "ready to blow". The RCM passes a small current limited test signal (just a few ma, it takes 5+ amps to light up the squib) through the squib to detect this resistance, and confirm that the air bag is connected and ready to go.

By placing the resistors across the harness connectors the RCM believes the air bags are there and "good to blow" while doing the test--a bit safer than doing the test (after the repair) with live explosives."

I'm thinking Ford probably didn't have 20 designs for this type of circuit, and that explanation sounds completely reasonable to me in every way.

Edit: ok, another quick search indicates that it's virtually universal across Ford airbags that the computer is looking for between 2 and 5 ohms. I think any standard value in the middle there should make the computer happy, like 2.7 ohms