I had a Chevrolet dealer (Bill Heard Chevrolet in Sugar Land, TX) try to screw me similarly.

I went in to have my air conditioner compressor replaced (it was under warranty, as they had put in a new one less than 9 months prior). Even though it was experiencing the exact same problems it did when they replaced it the first time, they claimed it was a completely different problem altogether.

THEN, my car was slow to start for them, which caused them to diagnose a failing fuel pump. Do you know what the real problem was? I WAS LOW ON GAS.

These f***ers tried to charge me $1,200 to fix two (nonexistent) problems, so I took it somewhere else for a second opinion, but not before they held my car hostage for a $70 diagnosis fee.

The mechanic I took it to said I had a minor leak in freon (from the compressor that the dealership, because of the warranty, should have serviced for FREE) and needed a new battery. I was fixed up for less than $100. LESS THAN $100! And the problems that the Chevrolet dealer dreamed up still wouldn't have done anything constructive, $1,200 later.

I chewed out the service manager and got my $70 diagnosis fee back, plus an apology. I'm currently in the process of shopping for a new car and I've avoided them like the plague.