I am considering a local 1990 300SEL. The owner said one problem is that the airbag has issues. He said he took it to our local Mercedes dealer and they stated that it (airbag) had a bad control unit and said the cost to repair would be $1200! Does this seem fair/right? What exactly is the "control unit" and what would cause it to go bad? Thanks in advance.

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2004 Toyota Sequoia Limited 4wd
1991 Lincoln Town Car Executive
1991 Cadillac Sedan DeVille
1988 Mercedes 300SEL
1972 Chevrolet Caprice Kingswood Estate 9-passenger wagon
1973 Pontiac Grand Ville
(Prior MB's: 1974 240D, 1985 380SE, 1984 190D, 1993 400SEL)

Walk away from this car. You don't even want to think about one that has air bag problems.

There are other 300-SELs.

Quite simply, it is the brains that decides when to activate the air bag(s) and seat belt tensioners (if the car has them) and your life could depend on its ability to make the proper decision.

The control unit measures the forces of decceleration acting on the vehicle. It can tell the difference between normal deceleration during braking, higher deceleration that lasts a very short time such, as bumping a car, and high deceleration that lasts a milliseconds longer, such a ramming a solid object at speed and crumpling the crush zones of the chassis.

Depending on its programming, it activates the seat belt tensioners, if they are installed, and the driver and passenger air bag.


Best Regards,
Jim

Thanks for the replies. He also said that the car uses a quart of oil between changes. Also has a busted taillamp lens, some sheetmetal damage at that light. Hear me walking? Thanks again!

I am not sure what the seller means by air-bag issues. Did they deploy at some time for no reason, where they part of a recall but never serviced?

I know you are considering an 85' 500 SEL like mine but can tell you that the day mine was sold off the showroom floor, it came with a recommendation to check and service the air-bag at 10 years. I doubt that ever happened. Even though seatbelt tensioners and air-bags work to the same end, your safety, they work independently. My 20 year old tensioners will still lock up if I deploy them too quickly but I would not bet money that my "depowered" air bag(pre-1997) will do the same even if my SRS check-light says it will. Does any manufacturer recommend a longer interval? This is a pretty sophisticated function to ask for it to be reliable much longer than that without inspection.

Compare them both, 85' 500 and 90' 300 very critically before you decide to walk away from either one. As far as airbags go, they may both have the same issues. OD miles and documented maintainence, including air-bags, are much better barometers of worthiness.

Once again, good luck