[Neel]

Sounds like a bad (or wrong) sending unit, from what you have described.. If you have an Ohmmeter, you can check the sending unit easily: Engine off, connect the meter to the connector on the sender, with the sender wire disconnected and the other end to ground.. Note the reading on the meter.. It should have a high ohmmeter reading ~ infinity ohms.. If you have a low reading, you have a bad/ wrong sender.. Also check to make sure your new sender has a bit of a 'bell' shape to it.. If it doesn't, they put the wrong sending unit in.. I can't imagine that happening, but the shop apparantly midiagnosed the original problem, so I guess anything can happen.. I hope this helps..