thanks for the advice, will double check for real heat and ac There could have been something under my seat that hit the crash sensor. I had new rotors in back, one fell behind and under seat, that could have caused issue. I had not even hit a big pothole at all, in past have hit many in ny area. Can the fuse be brought into dealer? can it be jumped? Does dealer need whole car, will I need to buy whole pyrofuse unit? Seems to say in text from above they can reset it.
The airbag-triggering accelerometers on cars are usually mounted in the front bumper area. A dropped heavy object will not trigger them in any case. Normally, one would expect the airbags to go off if an airbag sensor receives a sufficient acceleration. "Reactivate" can mean replace a part.
And yes, you can buy the pyrofuse or any other part from a dealer, or an internet-based MB parts seller - who may also rebuild the fuses for cheaper.
The sensors may not be the problem, the pyrofuse itself may be defective, and also, Smart 451 EDs seem to have a problem with wiring harness chafing failures - so the problem may be a broken wire, not the pyrofuse. But per my previous post, the continuity of the fuse connection can be checked easily enough. And yes, as MB DNA wrote, always disconnect the positive terminal of the 12V battery before disconnecting any connectors needed to remove the front seat or any airbag-related components (or any other electrical work for that matter).
Correct me if I'm wrong, but I get the impression from your questions that you don't have a lot of automotive repair experience. But I fully understand your trepidation about bringing it to a dealer - a lot of Smart Car repairs seem to be driven by MB's bureaucracy and lawyers, not practical mechanics or engineers - such as stories of people being told the car is a total loss (becasue the battery pack must be replaced) when a crash big enough to trigger the airbags/pyrofuse happens. What bull****! (are we allowed to say that word?)
(Edit: Oh, the forum automatically replaces the offending words with asterisks)