Daft question perhaps. My understanding in the event of accident is that an airbag would deploy if the seat is occupied but not deploy if the seat is empty. If, by unplugging the seatbelt detection does this operation become compromised?

If so, then would a car not potentially fail its MOT on the basis of the new check for defective SRS equipment?

gazz_bee said:

Daft question perhaps. My understanding in the event of accident is that an airbag would deploy if the seat is occupied but not deploy if the seat is empty. If, by unplugging the seatbelt detection does this operation become compromised?

If so, then would a car not potentially fail its MOT on the basis of the new check for defective SRS equipment?

Click to expand...

Not at all, drivers airbag will always deploy as its assumed the drivers seat will never be empty if the car is being driven

Most Easterly Pandas said:

Not at all, drivers airbag will always deploy as its assumed the drivers seat will never be empty if the car is being driven

Click to expand...

I had thought through that permutation which is why I didn't say driver's seat . . . .

However, my understanding (albeit from other manufacturers) is that the seat belt and occupancy sensors are used to calculate the airbag inflation/deflation rates in a given impact. A sensor with a false positive could cause incorrect inflation and I still wonder if this is an MOT fail.

gazz_bee said:

A sensor with a false positive could cause incorrect inflation and I still wonder if this is an MOT fail.

Click to expand...

Only if it causes a warning light to illuminate on the dash

Been thinking about this today .........

The alarm warning and indication on the dash are controlled by two switches in series fed by that light grey plug/socket under the seat.

As you sit on the seat, you make the seat detector contact to complete the circuit, so as you start the car, the dashboard light comes on and if you drive away, the alarm sounds.

However, as you connect your seatbelt buckle, the circuit is broken.

At this point, the dashboard indication goes out and as you drive away, the alarm is silent.

By disconnecting the light grey plug/socket, you are isolating completely the seat contact sensor and seatbelt switch. As far as the car itself is concerned, there's no-one sitting in the driving seat and the car is driving itself. :yum:

If I'm correct, by disconnecting the light grey plug/socket, it will have zero effect on any safety system.

As far as I'm aware, the airbag deployment is controlled by rapid deceleration or side impact etc and is autonomous, and as far as I'm aware, there isn't a pre-tensioner for the seatbelts in a Fiat 500 ............... but I am prepared to be proved wrong on these things.

Regards to all,
Mick

I was 99.9% sure there was a pretensioning system, but not sure where from now I think of it!

PS:

Just thinking again ..........

We have a 2001 Clio, and when it was fairly new, the airbag warning light came on. We took it to the Renault dealer to be sorted.

It turned out that there's some wires under the driver's seat that had become detached because they were dangling down, and those wires were to do with the seatbelt pretensioner. (The passenger side has no such luxury) By re-connecting the wires, all was well and the dealer chappy tucked the wires away out of harm's way too.

Now, when we switch on the ignition of our Fiat 500, the airbag warning comes on temporarily as you start up. When the engine is running, the airbag warning is extinguished ......... irrespective if the light grey plug/socket is connected or disconnected. ie it has no effect on the airbag system.

Am I right, or am I wrong?

Regards,
Mick.

Not exactly definitive, but http://www.ebay.co.uk/itm/FIAT-500-...arts_Vehicles_CarParts_SM&hash=item2a47034bb2

I would be very wary about doing what you are doing.

PPS:
The seatbelt pre-tensioner in a Clio is operated by the seatbelt buckle unit. It pulls downward as the airbag system deploys. You can see the wires, the mechanics and the electrics on the buckle unit. Looks to me that it would pull downwards two or three inches.

Our Fiat 500 has nothing like that. The seatbelt buckle is bolted solidly.

TTFN
Mick

If only there was somewhere else a pretensioner could be mounted (look at the ebay photos).

I humbly suggest that you don't understand this system nearly as well as you think you do.

It could be a case of "Oh, they'll never be not someone in the drivers seat, always fire the airbag" or it could be a case of "Well, unless there's definitely someone in the drivers seat why would we fire the airbag".

Given the stuff that came out into the reports of GM's ignition switch problems in the US causing airbags not to fire, I would give more credence to the second theory than it merits at first glance.

It could be either way. Is it really worth taking the risk?

zanes said:

........... Is it really worth taking the risk?

Click to expand...

I don't know!

At this point, all is connected normally. All I did was experiment and report my findings, then stew on it overnight.

I wonder that Fiat in their wisdom have made a system to warn you that your seatbelt isn't fastened. They are not unusual in having this system. It's simple and basic ........... or that's the way I see it.

However, just say you were stone deaf and couldn't give a toss about the warning light on the dash. Would Fiat install an airbag system that wouldn't deploy if you ignored the warning light and couldn't hear the alarm?

Does the passenger airbag deploy if there's no passenger sitting in the front passenger seat?

I don't know.

Regards,
Mick.

I can vouch for the early Mk3 Renault Clio having seatbelt pre-tensioners and air bags.

A few years ago I clipped a kerb which deployed only the passenger curtain airbag, but activated both front seatbelt pre-tensioners, load limiters and fuel cut off for what was an embarrassingly low speed incident. If there hadn't been a front passenger, no airbag would have deployed, I would have been been able to drive away and my insurance company would have been £2.5k better off.

Mick F said:

and as far as I'm aware, there isn't a pre-tensioner for the seatbelts in a Fiat 500 ............... but I am prepared to be proved wrong on these things.

Regards to all,
Mick

Click to expand...

Most cars for the last decade have had pretensioners, and the 500 has on the front. Its built into the inertia real, as photographed on that eBay listing

Yes, I see that, thanks.

I woke up this morning still stewing over this .........

I'm now of the opinion that the light grey plug/socket is ONLY for the seatbelt alarm and warning, and that the seat pressure sensor is a separate thing entirely.

No proof, just an opinion.

My thinking is thus:
Just say you are reversing and as such may have undone your seatbelt.
Suddenly, out of nowhere, a runaway vehicle slams into your car.

Just coz you have your seatbelt disconnected - no alarm because you are going slow and in reverse - it shouldn't preclude the airbag system going off and protecting you.

If I'm correct, the airbag system is energised by sitting on the seat, not by a combination of sitting on the seat and fastening your seatbelt as well. The two systems are separate.

Dunno for sure, just an opinion.

Regards,
Mick

After reading through this thread again, it seems to me that if buckling the seatbelt in before sitting on the seat is too much hassle (!), then getting a spare buckle from a scrappie and simply clicking it in while you are going up and down your long drive makes far more sense than messing about with the installed car electric circuitry.
With so many integrated systems in modern cars, and with the occasional alert Mot tester, plus the small print conscious insurance companies, tinkering with safety system electrics has hazards that plugging in a spare buckle does not.

Bear in mind that it would be plugged in as you leave the road on a homeward journey, and it would stay plugged in until you drive up to the gate again on the next outward journey, this seems no more of a problem than plugging in the ignition key.

Mick F said:

Yes, I see that, thanks.

I woke up this morning still stewing over this .........

I'm now of the opinion that the light grey plug/socket is ONLY for the seatbelt alarm and warning, and that the seat pressure sensor is a separate thing entirely.

No proof, just an opinion.

My thinking is thus:
Just say you are reversing and as such may have undone your seatbelt.
Suddenly, out of nowhere, a runaway vehicle slams into your car.

Just coz you have your seatbelt disconnected - no alarm because you are going slow and in reverse - it shouldn't preclude the airbag system going off and protecting you.

If I'm correct, the airbag system is energised by sitting on the seat, not by a combination of sitting on the seat and fastening your seatbelt as well. The two systems are separate.

Dunno for sure, just an opinion.

Regards,
Mick

Click to expand...

I believe you're correct, normally occupancy sensor is only on the passenger seat from memory and not on the drivers, and that is a separate wire (going back to how it is on Fiat Stilo's anyway).

Sweetsixteen said:

After reading through this thread again, it seems to me that if buckling the seatbelt in before sitting on the seat is too much hassle (!), then getting a spare buckle from a scrappie and simply clicking it in while you are going up and down your long drive makes far more sense than messing about with the installed car electric circuitry.
With so many integrated systems in modern cars, and with the occasional alert Mot tester, plus the small print conscious insurance companies, tinkering with safety system electrics has hazards that plugging in a spare buckle does not.

Bear in mind that it would be plugged in as you leave the road on a homeward journey, and it would stay plugged in until you drive up to the gate again on the next outward journey, this seems no more of a problem than plugging in the ignition key.

Click to expand...

You are totally correct of course.

My original question was:
Is there a way of disabling the seatbelt alarm?
I find it intrusive and un-necessary. A simple warning light would be enough.
I imagine finding the alarm sounder and cutting its wires.

I still hold by the fact that the alarm is intrusive and un-necessary, but I see that cutting wires or tinkering with the electrics is not a good thing to do.

I'm still stewing on this though.

Regards,
Mick.

Mick F said:

You are totally correct of course.

My original question was:
Is there a way of disabling the seatbelt alarm?
I find it intrusive and un-necessary. A simple warning light would be enough.
I imagine finding the alarm sounder and cutting its wires.

I still hold by the fact that the alarm is intrusive and un-necessary, but I see that cutting wires or tinkering with the electrics is not a good thing to do.

I'm still stewing on this though.



Regards,
Mick.

Click to expand...

I agree it's intrusive (well, it's designed to be...) and certainly in most cases unnecessary. If only it cut out after 10 seconds I wouldn't mind so much. I imagine the thinking is that the passenger can't see the light in the instrument binnacle and needs the reminder. I'm interested in whatever you may come up with.

On a related issue; I find myself repeatedly leaving the indicators on after less than 90 degree turns and not noticing, sometimes for many minutes, that I'm still flashing a turn. I imagine it's partly because the indicators only seem to cancel with a tight turn. This only happens in daylight because the reflection on the binnacle glass hides the lights and the quiet little 'tick-tick' can't get through the heavy-metal(!). It's a pity they aren't as intrusive as the seat-belt reminder.

In forty-odd years of driving this is the first car in which this has happened so regularly, I'm looking at fitting a louder beeper (or a flashing LED) but I'm uncertain about where to splice it in to the indicator cables. Has anyone considered this? Oh, and turning down the music isn't an option.

Mick F said:

My original question was:
Is there a way of disabling the seatbelt alarm.

Click to expand...

And it was answered on the second page....:bang:

Piccolo Nero e Bella said:

I agree it's intrusive (well, it's designed to be...) and certainly in most cases unnecessary. If only it cut out after 10 seconds I wouldn't mind so much.

Click to expand...

Interestingly on the Stilo is does stop after 90 seconds and leaves only the light illuminated.