The system is a common control unit with airbags (see Chapter On-board electrical equipment). Power is supplied to the drive mechanisms in the event of a frontal collision that causes an axial overload exceeding a certain value. Weaker impacts, as well as impacts from behind, do not trigger the system.
When the system is switched on, the gas inside the cylindrical modules of the tensioning mechanisms ignites. The piston is then abruptly moved forward, taking up the slack in the belt by pulling in its stem. The explosive force in the cylinder is calibrated so that when taking up the slack in the belt, the driver/passenger's body is pressed securely against the seat back without excessive jerking. After a single activation, the tensioning mechanism becomes unusable and must be replaced.
To avoid the risk of injury from unintentional activation of the tensioners during vehicle maintenance, particularly on the front seats, disconnect the negative battery cable and de-energize the belt tensioner system. To deactivate the tensioners, remove the SRS fuse from its socket in the fuse/relay box. Work may only begin after at least five minutes have passed since the fuse is removed, which is the time required for the reserve capacities in the SRS control unit to discharge.
When performing any maintenance work on the front seats of your vehicle, try to keep the following points in mind:
Attention! After the seat belt tensioning system has been triggered, both tensioning mechanisms must be replaced together with the control unit!
[This article is taken from the website RENAULTBOOK.ru]
Attention! An accidentally damaged tensioning mechanism cannot be installed on a vehicle and must be replaced even if there are no external signs of damage!
Caution! Do not allow tensioning mechanism components to come into contact with any solvents under any circumstances!
Warning! A sharp blow to the front seat may cause the seat belt tensioner to activate!
Caution! Do not allow the seat belt tensioners to become excessively hot!