Airbag control unit with part number A 004 820 24 10

What is the function of the airbag control unit 004 820 24 10?

The SRS control unit with part number 004 820 24 10 is an original Mercedes-Benz OEM component, specifically designed for the E-Class A124 Cabriolet. As the central control unit of the passive safety system, it monitors crash sensors and, in the event of a collision, deploys the airbags and activates the seatbelt pretensioners to protect occupants.

This control unit is a critical component for vehicle safety in the Mercedes-Benz A124 series (model years 1991–1997). It continuously processes data from acceleration sensors to detect a collision. In an emergency, it sends ignition signals to the appropriate restraint systems within milliseconds. Typically, the unit is installed beneath the center console.

It was manufactured by Mercedes-Benz AG, though related modules sometimes incorporated components from Bosch (e.g., 0285001060). Part number 004 820 24 10 is also equivalent to other numbers such as 004 820 17 10 and A0008207226, which serve the same purpose.

Why does the control unit 004 820 24 10 fail?

The primary causes of failure for the control unit 004 820 24 10 are age-related hardware defects. Due to the vehicle’s age—over 25–30 years—electronic components such as capacitors, sensors, or microcontrollers on the circuit board can fail. Vibrations and environmental factors also contribute to material fatigue and board malfunctions.

The electronics in these W124/A124 models have reached the end of their service life. Cold solder joints, corroded contacts, or defective memory chips are typical consequences of aging. These hardware issues prevent the control unit from performing its functions correctly, directly impacting safety.

Another potential cause of failure is a collision. Even if the airbags did not deploy, the intense forces involved in a crash can damage the sensitive electronics inside the unit, leading to internal faults.

How do you recognize a defect in 004 820 24 10?

A defect in the control unit 004 820 24 10 is most clearly indicated by the airbag or SRS warning light remaining constantly illuminated on the instrument cluster. Another clear symptom is the complete loss of communication between the control unit and diagnostic tools, making it impossible to read or erase fault codes.

The most common sign is the activated SRS warning light that fails to turn off after starting the engine. This indicates a critical fault in the restraint system, jeopardizing passenger safety. In the event of a crash, the airbags and seatbelt pretensioners may no longer function properly.

In the workshop, the defect often manifests as a missing connection to the diagnostic tool. Technicians find that the control unit is unresponsive. A specific technical indicator seen in these models is, for example, the absence of power at pin 6 of the fault memory connector.

Sometimes, fault codes can be read but cannot be permanently cleared—they reappear immediately, pointing to an internal hardware issue within the control unit itself that cannot be resolved simply by resetting the system.

In which vehicles is 004 820 24 10 installed?

The airbag control unit 004 820 24 10 is primarily installed in the Mercedes-Benz E-Class A124 Cabriolet from model years 1991 to 1997. It is also compatible with other models in the W124 series, including sedans, coupés, and T-models, especially in the E 200 and E 220 engine variants.

At Airbag24, we repair the control unit with part number 004 820 24 10 for the following Mercedes-Benz models:

Mercedes-Benz: E-Class A124 Cabriolet (e.g., E 200 Cabriolet 124.060, E 220 Cabriolet 124.062), as well as other W124 variants (e.g., E 200 Sedan 124.019).

Is repairing 004 820 24 10 worthwhile?

Yes, repair is the most economical and sustainable solution. Compared to a new part, which often costs over 800 euros, repair offers significant savings. Additionally, the original control unit remains intact, avoiding compatibility and coding issues while restoring full functionality.

An original new part is not only expensive—for classic models like the A124, availability can also be limited. Repair provides a quick and reliable alternative here. For instance, a comparable new part such as A0018201926 from Mercedes-Benz costs around 878 euros, whereas repair is considerably cheaper.

Used parts from platforms like classified ads carry high risks. They are often just as old as the defective component, come without warranty, and may already harbor undetected pre-existing damage. In contrast, professional repair with 2 years’ statutory liability for defects ensures reliability and a long-term solution.

How does the repair process work at Airbag24?

Upon receiving the control unit at Airbag24, our technicians perform a detailed analysis to identify the exact cause of the fault. The repair involves replacing defective electronic components on the circuit board. A comprehensive functional test then ensures that the device is fully operational again.

The process begins with removing the control unit from the vehicle, typically located beneath the center console. After submission, the unit is opened and the circuit board is inspected for visible damage using specialized measuring instruments.

Defective components—such as aging capacitors, sensors, or faulty microcontrollers—are carefully desoldered and replaced with new, high-quality parts. Following repair, proper communication and functionality are simulated on a test bench to guarantee flawless operation. We provide 2 years' statutory liability for defects on every repair.