Mercedes-Benz E420 Air Bag Clockspring Replacement Cost

The airbag clock spring is designed to last the lifetime of the vehicle. On some older models, the wiring inside the clock spring can become brittle and break over time, causing failure. The clock spring may need to be replaced if it is damaged during careless service to the steering system, and, in some cases, if the vehicle is in a crash and the driver's airbag deploys.

A technician will use a scan tool to check the electrical system for signs of a faulty airbag clock spring. A test with a multimeter may also be done on the clock spring itself. A repair manual and wiring diagram are used to identify and test each circuit running through the clock spring.

To replace an airbag clock spring, a technician will first disconnect the battery to disarm the Supplemental Restraint System. The driver's airbag and the steering wheel are removed. In order to access the wiring harness connected to the airbag clock spring, the trim components on the steering column are removed. It may also be necessary to remove trim components from the lower dash assembly for access to the harness plugs. With the trim removed and the clock spring harness disconnected, the clock spring is removed and replaced. After the clock spring, steering wheel, trim, and airbag have been installed and connected, the Supplemental Restraint System will need to be reset with special software.

If the airbag clock spring is damaged or defective, the Supplemental Restraint System is usually disarmed and the airbags will not inflate in the event of a vehicle crash. Furthermore, a short circuit in the clock spring can result in additional damage to the vehicle's electrical system or computer modules. If the airbag (SRS) warning light illuminates on the dashboard, or if any other symptoms of airbag clock spring failure appear (i.e. faulty radio controls on the steering wheel), RepairPal recommends having the vehicle evaluated and repairs completed by an experienced technician as soon as possible.

The airbag clock spring contains delicate wires that can be damaged during careless service to the steering and front suspension systems. Care must be exercised to ensure that the steering wheel is not allowed to free-spin with steering and suspension components disconnected. The battery should always be disconnected prior to performing any repairs on the Supplemental Restraint System, including the airbag clock spring. Care must be exercised whenever handling an airbag module. The SRS will also need to be reset once repairs have been completed.

It is recommended that repairs to the Supplemental Restraint System be left to a professional. Accurate diagnosis of the system is essential. Depending on the reason for failure of the airbag clock spring, other components may also need to be replaced to ensure proper function of the Supplemental Restraint System. A professional technician will have access to the equipment to perform a thorough test of the system for any other failed components and replace them as necessary. A technician will also be able to reset the system with special software after the components have been replaced. Someone with advanced DIY experience may be able to perform part of the repair, but will still need assistance to reset the SRS.