Mercedes-Benz SL-Class R107 Convertible airbag control unit repair

What is a Mercedes-Benz SL-Class R107 Convertible airbag control unit?

The Mercedes-Benz SL-Class R107 Convertible airbag control unit is the control module of the SRS system that Mercedes-Benz offered as an option for the R107 from the 1985 facelift onwards. It evaluates the crash sensor and, in a frontal collision, fires the driver airbag and the belt tensioners. Without a working control unit the entire restraint system stays switched off.

The car uses a Bosch control unit in an aluminium housing – the same family of units that also worked in the S-Class W126 and the W124 of those years. It is one of the very first airbag control units and is now 35 to 40 years old.

The unit monitors the firing circuits, the vehicle voltage and its own energy reserve. If it detects a fault, it switches on the SRS warning lamp in the instrument cluster and deactivates the system until the cause has been fixed.

Why is the Mercedes-Benz SL-Class R107 Convertible airbag control unit defective?

On the R107 the cause is almost always age: capacitors in the energy reserve dry out, solder joints crack from vibration and temperature cycles, and the connector contacts corrode. After an accident with deployment the control unit also stores crash data and locks itself.

Electrolytic capacitors from the 1980s have long exceeded their service life. Once the internal energy reserve loses capacity, the control unit reports a fault even though the airbag and belt tensioners themselves are fine.

Other causes are overvoltage from battery chargers or jump-starting, moisture in the footwell and voltage spikes during work on the vehicle electrics. New units for the R107 are hardly available from Mercedes-Benz any more – repairing the original unit is therefore the usual way to bring the system back into service.

Common fault codes in Mercedes-Benz SL-Class R107 Convertible airbag control unit repair

The R107 control unit has no fault memory with codes like today's OBD vehicles. The message is the SRS warning lamp: if it stays on after the self-test when the ignition is switched on, the control unit has detected a fault and shut the system down.

• SRS lamp stays on permanently after starting → the control unit has detected an internal fault or a fault in a firing circuit
• SRS lamp only comes on after a few minutes of driving → typical of aged capacitors and cold solder joints that fail as they warm up
• SRS lamp stays dark during the self-test → control unit without supply, lamp defective or control unit not working
• No communication – control unit is defective → the workshop tester cannot connect to the control unit

A specialist workshop narrows the fault down on the vehicle. If the control unit remains as the cause, send it to Airbag24 for testing or repair – we test it on the bench and name the defect before any repair is carried out.

Which part numbers exist for Mercedes-Benz SL-Class R107 Convertible airbag control unit repair?

The Mercedes part number of the R107 airbag control unit is 003 820 73 10 (A0038207310). The manufacturer is Bosch; the Bosch number 0 285 001 014 is also printed on the housing. Both numbers refer to the same unit.

The number is printed on the aluminium lid of the control unit, directly below the Bosch lettering and the "SRS AIRBAG" print. Sister units of the same design carry numbers from the 003 820 xx 10 range, for example 003 820 74 10 in the S-Class W126 – they are not simply interchangeable. All offers for this number are collected on the part number page.

Airbag24 has been repairing airbag control units for more than 20 years – over 20,000 repaired units, TÜV-safe, usually within 3–4 working days. Select the appropriate repair type above and create the repair order; express repair is available on request.