Airbag warning light on Punto MK-II

Looks like it's going to be either £75 for an analysis by Reg Vardy or £55 from my local independent. Minimum of 1 hour labour apparently, they need to run an extensive list of tests. I hope this is the case and they don't just strap up a computer and reset the alarm. I'm going to try the local independent as they're more convenient. The guy seemed to suggest that most airbag systems were similar for test and repair.

I'm guessing from what I've read, I should unplug the battery negative and leave for at least 10 minutes before touching anything around that area. That should reduce the chance of tripping the airbag ECU. An expensive lesson to learn.

Thanks

Tim

SteveH expressed precisely :

They store their own current source for some time, hence the suggestion (not mine) of leaving the battery disconnected for 30 minutes. Hence shorting the terminals would not help, though simply turning the lights on would do exactly the same.

Tim used his keyboard to write :

The usual recommendation is 30 minutes as a minimum. That is before going near any part of the air bag system for both its and your safety. If accidently triggered they can cause serious injury.

How on earth would that happen?

The capacitor the air bag uses would not be on the same circuit as any lights I could think of...

Chris

If you disconnect the battery, and the airbag +ve terminal is connected to the +ve battery lead, as is the light +ve terminal, and the airbag -ve terminal is connected to the chassis along with the light -ve terminal, turning the lights on would be equivalent to shorting the airbag +ve/-ve terminals together via a rather small resistance. Unless there's normally some form of isolation between the battery leads and the airbag capacitor, which is quite possible.

Harry Bloomfield ( snipped-for-privacy@tiscali.co.uk) gurgled happily, sounding much like they were saying :

The usual recommendation for minimum time appears to be a cuppa and a chinwag...

I wasn't actually suggesting the capacitor would be in the same circuit as the lights, rather that it would be pointless shorting the battery terms and that the same effect can be obtained by simply turning the lights on - in other words the lights would discharge any remain voltage which might be appear across the battery leads, but that it would not make the air bag system safe to disturb.

The capacitor or similar is in the air bag unit, taking its charge from the main battery, is there to ensure the air bag is still able operate even if the main battery supply is lost in the event of an accident, even if the main battery leads are shorted out during the accident. Hence the need for the 30minute delay to permit it to discharge.

Hope that is a little clearer?

David Taylor laid this down on his screen :

The two circuits are isolated by a diode, which permits the air bag system to charge up from the main battery, but not to discharge.

Right, I see what you meant.

Yes, I knew that thanks :-)

Much.

Chris

Got it done at the local independent today. £56.40 inc VAT. The warning light was flashing due to the Airbag ECU seeing a fault with the warning light i.e. when I took the instrument panel off and started the car. Well live and learn eh?

Still the amount of work I had to do over the weekend, I'm still probably up by £50-100 labour charge.

I've read in a few places 10 minutes, but if you're doing the work at home disconnecting the battery 30 minutes before working isn't a major issue.

One of the chaps at work brought in his OBD-II connector and we tried it with

Regards,

Tim

The wife and I were discussing this. Not a usual point of conversation, but a couple of flashing lights prompted it. She'd read somewhere that an airbag will break your nose, or at the very least leave you with a couple of black eyes. I figured that probably wouldn't be the case in a non-crash situation as you're not being propelled forward at the same time. I had heard that the noise of the explosion can cause ruptured ear drums.

I'm sure if you were working close the steering wheel (i.e. trying to remove the airbag), you'd certainly know about it going off.

Makes you wonder if they are calibrated to simply go off, or if they are capable of determining the pressure of the gas in the bag. The only reason I think of this, is you can see some (typically) women sat bolt upright only a foot or two away from the steering wheel. Without the ability to control the size, volume or pressure of the airbag, there might be greater risk of physical injury in this position.

Regards,

Tim

Well I sit quite far away from the wheel, & the main complaint I had was that they smell bad, wheras Metro steering wheels literally scalp you

Some of the expensive newer cars do do this.

I didn't mention the necessity of using a dealer necessarily, just a competant garage, and not DIY, especially if one is not adept in dismantling and reassembling pretty critical components.

Depends on the age and manufacturer of the car as to how complicated the airbag components are. I was suggesting that if you fiddle about yourself, there's a (minute risk) of setting it off, and getting some nice black eyes and a broken nose, or a very sore neck, or ... etc.

Plus, they go off so quick, you have no time to react. So even if you were working to the side of it, you'd still pooh yourself when it goes off :)

Tim wrote in news:UN%Ch.23292$z54.10996@newsfe3- gui.ntli.net:

conversation,

As long as you're far away enough to give the bag room to inflate, it shouldn't matter. Once the front end has crumpled enough to reach the sensor, the bag fully inflates within a few 100ths of a second via it's explosive charge. So it should always been fully inflated before the body hits it. When the body makes contact, the air is forced back out via ventilation holes. Hence the timing and rate of the deflation are controlled via the size of the ventilation holes, not by the vehicle speed or proximity of the person to the wheel/dashboard etc.

There was a programme about them on Discovery the other day. Virtually all of them made by the same company - Autolief in Switzerland.

Stu

I once advised a small female relative to get their airbag turned off because her driving position was ridiculously close to the wheel (15cm at a guess). They didn't however! I'd imagine that if your head hits the airbag while it's still expanding it'll do you no good at all.

Typically how much do they expand past the front of the wheel?

Peter.

Peter Spikings wrote in news: snipped-for-privacy@peter.power.net.uk:

Dunno, but I would guess that 6 inch is a bit too close for comfort. In any case, that's a ridiculous position to adopt - imagine the difficulty it would cause if an emergency arose, e.g. if a child ran out and a sharp swerve was required. No doubt having ones hands so close to the chest would deny the ability to work the wheel quickly enough.

Unfortunately, it seems to be a position that many women drivers adopt. I believe it's because they find it necessary to be able to see the bonnet in order to have the confidence to drive the car. IME, I've noted that a lot of middle-laners and drivers who display a general lack of confidence can be seen adopting that position, so when I see a 'wheel hugger', I tend to extend them the same courtesy and tolerance as one would with a learner driver. My own wife has been driving many years, yet she still sits on a cushion and lacks the courage to drive on a motorway or anywhere outside our home town ;-)

Stu

Hmm, my mother sits that close in order to be able to operate the pedals.

Indeed.

That's seems like a decent theory.

I can't stand middle laners! What's worse is when people use the right hand lane of a duel carriageway going 40mph because they are turning right in 5 miles - there's a woman who lives near me and works near where I do that does this and we both leave at the same time!

Out of interest, what approach to people take when confronted with that sort of thing? I'm in two minds as to whether undertaking is OK if you're convinced that the lane hogger is not going to suddenly return to the left lane.

I have to admit, that while I do cut a lot of slack to learners (and P- platers) I kind of expect people who have been driving for a while to not *unnecessarily* hold me up, like when they don't want to drive at the normal speed for a road but then don't pull over occasionally when they acquire a long tail of cars that can't overtake. Or the afore- mentioned lane hogging.

Peter.