Your non-diagnostic vehicle-related problems solved by Steve Rothwell
Airbag article
Q On reading the article airbags, EVAP, misfires and wiper switch (CM Help!, January 2022, p78, VW EOS) I refer to the connection and re-connection of battery earth. The OP refers to ignition being on for both disconnect and reconnect of earth. You refer to Autodata and VAG as to ‘OFF’ when disconnecting the battery earth, ‘ON’ when reconnecting the battery earth. This may prevent power surges.
Can you expand a little please on this statement and indeed is it correct?
A As mentioned in the article, it is the advice given by both VAG and Autodata that when reconnecting the battery, the ignition should be on, as this may prevent power surges. As this is advice from VAG (VW) and is correct then I suspect that they have good reasons for the advice. I can only surmise that the design of the electrical circuits is more conducive to allowing the current to flow on the connection of the battery with the ignition switch in the 'ON' position.
Like many procedures in the workshop manual, this process should be followed because it is given by the manufacturer and I am sure that in most cases simply re-connecting the battery with the ignition 'OFF' would cause no detrimental effect, but as this procedure has been outlined, it would be foolish not to abide by it.
The main reason for this may be that if the airbag were to be triggered by a rouge system, it would be better to have the airbag triggered when the battery was connected and the vehicle unoccupied than when the ignition was first switched on
