Any second-hand car can give you problems, and this era of Mercedes-Benz production was not exactly notable for its build quality or reliability. On the other hand, that’s an insanely small amount of money for a convertible with a Mercedes-Benz badge, isn’t it?

The first thing to check is the overall condition. You say it’s a 7 out of 10 car, so presumably it’s showing its age in a few areas. Make sure everything electrical works properly and don’t forget things like the air-conditioning and cruise-control, both of which can cost a bomb to put right. Make extra sure the convertible roof works as it should, and check for wind noise from the roof at speed which could indicate an alignment problem. These roofs can easily be knocked out of whack in a rear end or side-on crash, so it’s vital everything lines up. The service record is crucial in a car like this, too. If there’s evidence of skipped maintenance, think long and hard about the purchase. These cars are complex and won’t tolerate sloppy servicing.

So why are cars like his so cheap? Mainly because people are scared that any repairs or parts needed will cost the earth. And there’s a fair bit to justify those concerns. Even apparently simple things like the dashboard vents are often complex, vacuum operated horrors in this era of European luxury cars, and can destroy your household budget to repair. But if you can set aside some money for repairs, and you are prepared to walk away from the thing if it all gets too hard (and expensive) then there’s a lot to like about a second-hand luxury car. Especially one that cost about $120,000km on the road when brand new and is now available for a fraction of that.

You're clearly not getting anywhere with the dealership, which appear to have given up on you. It's time to take your complaint further up the company tree and contact Mercedes-Benz directly. Ask them to have a technician from head office assess your car. Phone them on 1300 730 200.

Go back to the dealer and explain your frustration to him and request again that they be fixed. Should that not achieve the outcome you want take your complaint higher and go directly to Mercedes-Benz itself. I am sure if you do that you will receive the service you believe you are entitled to.