Airbag Clock Spring Problems
A supplemental inflatable restraint system on modern automobiles can have a large number of airbags installed throughout. The driver side airbag mounted in the steering wheel is the only one that uses a moving part. Airbags are inflated or deployed by the rapid expansion of gas. The gas is fired by an igniter commonly called a squib. The power reaches this component through a device called a clock spring.
It is the responsibility of this part to supply power for airbag deployment regardless of the steering wheel position. This means as the wheel turns electrical contacts must be maintained and this is done through a wound band of metal that looks like a clock spring. With the amount of movement in the steering wheel and the extended life of today’s automobiles it’s not surprising to run into problems with this component. This article discusses some symptoms and solutions for diagnosing and repairing airbag clock spring problems.
Clock Spring Location
The clock spring is located between the steering wheel and the steering column. With the airbag mounted in the center of the steering wheel it’s the job of the clock spring to supply voltage at all times to the module at any steering wheel position. The component is powered by wires that run down the steering column in a yellow conduit so they are easily identified. All SIR (supplemental inflatable restraint) connectors are also marked with yellow.
The other end is connected to the module through a coiled copper ribbon. When the steering wheel is turned this ribbon coils and uncoils without breaking its electrical connection. It gets its name because it is very similar to what you see when you remove the back of an old fashion wind up wristwatch or clock.
Common Clock Spring Problems
If you can imagine how often the airbag spring needs to coil and uncoil to maintain its connection as the wheel is turned from left to right, than you can also imagine after 10 years of operation problems could develop. One of the most common complaints is a clicking or scraping noise while steering. This can be more evident in a parallel parking situation where the wheel is turned from full left to full right.
The problem can be isolated to just noise or can be accompanied with an airbag warning light illuminated on the dash. Some vehicle manufacturers run other accessories through the clock spring like the horn, radio control buttons and turn signals. Intermittent operation of these systems along with noise or airbag problems can often be traced back to clock spring malfunctions. No lubrication or maintenance is recommended so problems with this component usually lead to replacement.
Airbag Warning Light
The clock spring supplying power to the driver side airbag goes through a diagnostic self test when the ignition is switched on. The body control module sends out a reference voltage to verify the integrity of the connection through the spring. If this self test fails the airbag light will be turned on. Unfortunately codes set are not standardized as they are with OBD II (on board diagnostics system second-generation). Codes are referred to as manufacturer specific as each car maker will have different codes standing for different failures within the airbag system.
How to Replace an Airbag Clock Spring
Because of its location the replacement procedure is not easy or recommended as a do-it-yourself repair for several reasons. It is possible for accidental deployment of the bag while you’re working on the system. Although this is not common it’s dangerous enough that a professional is recommended to replace the part. Disconnecting the battery is not always sufficient for removing the danger because electrical energy can be stored in a capacitor for emergency situations.
The first step in the procedure after disconnecting the battery and draining the capacitor is to remove the driver side bag and module assembly. After these steps are completed the task becomes much safer but not easier. The next step is to remove the steering wheel which can be very difficult and special tools are recommended because the wheel is pressed on to the steering column shaft. Once the steering wheel is removed replacement of the clock spring is straightforward with just a few screws and electrical connectors standing in the way of replacement.
There are a lot of electrical parts, sensors and modules in a modern airbag system. One of the few moving parts is the clock spring that supplies power to the driver side airbag module in the steering wheel. Since this part coils and uncoils thousands of times it can eventually wear out. Often the first signs of problems are scraping or popping noises from the column area.
Another indication of the failure would be an illuminated airbag light. Old cars with first-generation systems from the 80s and early 90s didn’t have access to the latest technologies available today. Couple this with the additional wear and tear from age and you can bet the older the vehicle the more likely a clock spring problem will occur.