My air bag light started to intermittantly come on about 6 months ago (bizarrly seemed to be related to cabin temperature) but has got to the point it is permanently on. The local garage read the fault codes and it indicated 3 faults the side bags, and curtain. They re-made the joints under the seats which cleared the faults on the side bags. Despite re-making some of the connections to the curtain air bag the fault is still present. They suspect the unit itself.
without payig out to get a new one is there a know resistance that could be put in place of the unit to determine if it is the unit or a fault elsewhere in the loom between the ECU and the unit at the back.