What Do Airbags Do?
Airbags are supplemental restraint system (SRS) devices that inflate almost instantaneously in a crash to cushion the occupant's head and upper body from impact with hard interior surfaces — the steering wheel, dashboard, door pillar, or window.
The word "supplemental" is important: airbags are designed to supplement a fastened seat belt, not replace it. An unbelted occupant can be fatally injured by a deploying airbag because the inflation speed (~300 km/h) means the bag hits the occupant before they have moved into the "cushion" zone.
Where Are Airbags Located?
Modern NZ vehicles typically have multiple airbags:
| Airbag | Location | Protects |
|---|---|---|
| Driver frontal | Steering wheel hub | Driver's head/chest in frontal crash |
| Passenger frontal | Dashboard | Front passenger in frontal crash |
| Side curtain | Headliner, deploys downward | Head in side impact or rollover |
| Front side/torso | Door or seat bolster | Thorax in side impact |
| Knee airbag | Dashboard lower section | Driver's knees/legs |
| Rear side | Rear door or rear seat | Rear occupants in side impact |
A Toyota Hilux or Mazda Demio may have 6–8 airbags; a more basic vehicle may have just the two frontal bags.
How Do Airbags Deploy?
- Crash sensors (accelerometers) detect sudden deceleration beyond a threshold (roughly equivalent to hitting a solid wall at 20–30 km/h)
- The airbag control module (ACM) evaluates signals from multiple sensors and decides whether deployment is warranted
- An electrical signal triggers a pyrotechnic inflator inside the airbag module
- The inflator burns a gas-producing propellant (typically sodium azide or newer alternatives), generating nitrogen gas
- The bag inflates in 20–30 milliseconds — faster than a blink
- The bag deflates through vents almost immediately afterward, allowing the occupant to move
The entire deployment and deflation takes about 100 milliseconds. Airbags are not cushions that remain inflated — they deploy and deflate before you finish blinking.
The Takata Airbag Recall
New Zealand was significantly affected by the global Takata airbag recall — the largest automotive recall in history. Faulty Takata inflators could rupture and spray metal fragments into the cabin instead of safely inflating the bag. This defect has caused multiple deaths worldwide.
Check your vehicle at the NZTA recall portal (search "Takata airbag recall NZ") or the manufacturer's website using your VIN. If your vehicle is subject to this recall, the remedy is free — contact your nearest authorised dealer. Do not ignore this recall.
What Does the Airbag Warning Light Mean?
The airbag warning light (SRS light) looks like a side-view of a person with a circle (representing an inflating airbag) in front of them. It illuminates briefly at startup as a self-check, then goes out. If it stays on or comes on while driving:
The airbag system has detected a fault and may not deploy in a crash.
This is serious. Common causes include:
- Faulty clock spring — a coil of flat wire behind the steering wheel that maintains the electrical connection to the driver's airbag as the wheel turns. A broken clock spring is one of the most common airbag faults
- Low battery voltage — the SRS module monitors battery voltage; a weak battery can trigger false faults
- Seat belt pretensioner fault — pretensioners are part of the SRS system
- Airbag module fault — the control unit itself has detected an internal error
- Crash sensor fault — a damaged or failed sensor
- Deployed airbag not replaced — after a crash where airbags deployed, the system will show a fault until all components are replaced
WoF and the Airbag Light
An illuminated SRS/airbag warning light is an automatic WoF failure in New Zealand. NZTA requires all fitted safety systems to be operational.
Do not attempt to clear the airbag warning light without diagnosing and fixing the underlying fault. Some workshops can clear the fault code with a scan tool without repairing the actual problem — this passes a WoF but leaves you with a non-functional airbag. This is both dangerous and potentially fraudulent.
How Much Does Airbag System Repair Cost in NZ?
| Repair | Estimated NZD Cost |
|---|---|
| Clock spring replacement | $200–$450 |
| Airbag module reset (after minor crash) | $150–$300 |
| Airbag module replacement | $400–$900+ |
| Crash sensor replacement | $150–$400 |
| Deployed airbag replacement (per bag) | $600–$1,500+ |
A car that has had airbags deploy in a crash can cost thousands to restore to full SRS functionality — always consider this in a post-crash repair assessment.
When to Book a Mechanic
Book within a few days if the airbag light comes on. Do not delay — you are driving a vehicle whose primary crash protection system may not function. Avoid high-risk driving situations (motorways, bad weather) in a vehicle with a faulted airbag system.