Has anybody seen this recurring fault with the BMW airbag system. The fault manifests itself with the airbag warning light failing to go off after the car is started.
I'm now up to the 4th visit to the dealership to see if I can get it rectified. So far they have replaced the microswitch under the passenger seat twice and tried to clean the contacts for the airbags.
Has anybody else seen or had this problem??? I'd like to prove it isn't an isolated incident/fault
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I follow most of the UK and American BMW forums, and have not seen mention of this problem anywhere, and would think your experience is an isolated incident. If its any consolation, BeeM`s generally suffer far fewer electrical problems than M.Benz. I will however keep my eyes peeled and if I see any reports, will update this thread.
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"BeeM`s generally suffer far fewer electrical problems than M.Benz"
That's a strange statement to make - what's your evidence? In my experience (of repairing electrical systems on considerable numbers of both maker's cars) the BMW suffer far more problems, in part because most BMW's have more electronics on them than MB. The older series BMW's in particular (e.g. E32, E34 models) were an electrical nightmare, and the newer ones certainly have their weak spots. At one time, a few years back, I had a nice little sideline repairing the instrument packs and 'check control' modules for a local BMW specilist.
In response to the specific airbag problem, the issue is likely to come down to excessive resistance on either the sensing or firing circuits. When the system initialises it passes a small sensing current through the firing circuit. This current (as per Ohm's law) will produce a voltage drop due to resistances of the connectors and the firing squibs. If the voltage drop is outside of specification (resistance too high or too low) then the warning light is illuminated. Similarly, the sensors are subject to a self-test (although this is a little more complicated than a simple resistance check).
Actually locating the fault could prove difficult since it is not good practice to take resistance measurements using conventional measurement instruments (dangerous..).
The connectors are gold plated and unless damaged or contaminated are unlikely to be at fault. Wiring damage is a possibility, or you could have an out-of-spec firing module. If any accessories have been fitted, or any electrical repairs have been carried out, then check for damage/disruption of the airbag wiring (yellow sheathed). Also, have you had any body damage or body repairs? It is possible that a sensor could have been damaged.
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"That's a strange statement to make - what's your evidence? In my experience (of repairing electrical systems on considerable numbers of both maker's cars) the BMW suffer far more problems, in part because most BMW's have more electronics on them than MB. The older series BMW's in particular (e.g. E32, E34 models) were an electrical nightmare, and the newer ones certainly have their weak spots. At one time, a few years back, I had a nice little sideline repairing the instrument packs and 'check control' modules for a local BMW specilist."
My comments were not directed at late eighties/early nineties production models, when M.Benz were supremely reliable, but at their current model range. My information is gleaned from friends who run M.B`s and my son, who works for an international I.T. company, where the car pool of approx 90 cars, is equally divided between BeeM`s and Mercs, and where his colleagues Benz`s are being plagued with various electrical problems, and in some cases spending several days in main dealers for rectification.
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False airbag light activation affects most car marques......
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