you probably think that is a strange title for a post here !
Hello, first post.
I know nothing of electronics, not bad with auto electrics being a qualified LPG installer and having worked on Harvesting machinery for years.
My car is a BMW 540 Touring. These have rear air suspension as standard, being a system to provide self levelling regardless of load. Both sides of the axle are fitted with a "level control" and these feed to a control unit. I know the suspension height can be altered via dealer level diagnostic interfaces and that its normal operation is "overseen" by the car ECU systems.
[more details here
WDS BMW Wiring Diagram System - 5 E39 from 09/98
under Chassis>Springing and damping>Single axle air suspension EHC>EHC supply>Rear axle air suspension level control ]
I can see from that site that the level control devices at the axle are Hall Effect units and I am wondering (in my simplistic way of thinking!) if the signal from those to the control unit could be altered into fooling the control unit to set the car at an alternative higher ride height.
My previous 5 series was a saloon with wheels that allowed the fittment of snow chains. My present Touring is a Sport model and BMW quote that this cannot be fitted with snow chains. Having looked at mine and spoken to several other owners on Forums the "clearance issues" that BMW cite as the reason are actually that it is physically very difficult to fit chains due to clearance for your hands rather than any issues in driving with chains on.
So what struck me was could I have a two position switch which would send the level control signals via "something" that would give a raised height when required so that chains could be easier to fit.
I may be way of the mark but I'm thinking that the Hall Effect units send a differing voltage to the control unit and the control unit, either directly or via the ECU, allows pressure in or out of the air springs as required. If the "something" altered that voltage then the car would settle at a different height and the rest of the BMW systems would be none the wiser...............................
Sorry this post is long and I hope I'm not wasting your time by talking rubbish.
Thanks
Iain