Airbag control unit with part number A1779009515

What does the airbag control unit A1779009515 do?

The airbag control unit A1779009515 is the central control unit of the restraint system (SRS) for Mercedes-Benz. It evaluates the signals from the crash sensors, decides in a crash within fractions of a second on the triggering of airbags and seatbelt pretensioners, and monitors the system continuously. If it detects a fault, it displays it via the airbag warning light.

After an accident the unit stores crash data and locks itself. It has no display of its own; its findings appear in the instrument cluster and can be read out with a diagnostic tool.

The electronics work in the background, without you noticing anything in daily life. That is precisely why their condition after an incident is so important for safety in the vehicle.

Why does the control unit A1779009515 fail?

The most common cause is stored crash data after an accident, even if no airbag was triggered; a normal diagnostic tool cannot erase them. Aged electronic components, cold solder joints, moisture and corrosion on plug connections, and voltage spikes, for example from a weak battery or a jump start, are also possible.

That no airbag fired does not mean nothing was stored in the control unit. The other causes develop over a longer period: a plug contact that has absorbed moisture, or a solder joint that gives way, does not become noticeable from one day to the next.

How can you tell that the A1779009515 is defective?

The airbag warning light in the instrument cluster lights up permanently or intermittently, an error message appears in the instrument cluster, the diagnostic tool finds no connection to the control unit, or the fault memory cannot be cleared. With such signs, airbags and seatbelt pretensioners may possibly not trigger in an emergency.

The light is the clearest hint the vehicle gives. If it lights up, a prompt check is recommended.

Which vehicles is the A1779009515 fitted in?

The control unit A1779009515 is fitted in these vehicles: Mercedes-Benz A-Class W177 (from 2018).

The assignment in detail:

• Mercedes-Benz A-Class W177 (from 2018)

Compare the part number on the label of the removed unit with this page; that only establishes that it is the right unit. Also have the fault memory read out beforehand, because only the log shows whether the control unit is defective or whether a plug or cable is the cause.

For the same vehicles, we also repair control units with the part numbers 0 285 015 019, 0285020871, A 177 900 03 04, A1779027906, A2479013703, A2479018801.

How does the repair of the A1779009515 work?

In the repair of the A1779009515 you first read out the fault memory and enclose the log. Then you disconnect the battery and only afterwards remove the control unit. Online you create the repair order and send the unit in well packed. Airbag24 checks it on the test bench, replaces defective components, erases stored crash data and carries out a function test, after which your own unit goes back.

This sequence is mandatory for safety reasons. Processing at Airbag24 usually takes 3–4 working days and concerns only the testing, repairing and checking.

Our repairs come with 2 years' statutory liability for defects. The repaired control unit comes back with all vehicle data and is ready for use as soon as it is refitted — no coding or programming is required.

How does the control unit A1779009515 get to Airbag24?

You send the control unit A1779009515 in as a parcel or book a UPS collection for an extra charge. After the repair, Airbag24 returns it to you by UPS.

The printed repair order goes into the parcel; you pack the unit shock-resistant.