20 miles is definatly their fault. I dont care if they did recommend it and you denied it. For it to go out that quick then it must have been really bad and they should have denied doing the work as they should have expected it to happen. I really think they did'nt install it correctly as "vizlay" mentioned, they are difficult to install and even a good mechanic can screw up cuasing this exact issue. If I wasn't a mechanic and was in your shoes and had no other option, I'd take it to a dealer and have them document what they see. If the dealer tells you the tensioner is blown then that answers your question but if the Hyundai certified technician doesn't believe that was the cause then he will document it as installation error and you could use that to your advantage. In California they have BAR (Bereau of automotive repair) to handle such cases, though I dont know about your area.
QUOTE (katte @ Oct 29 2009, 01:08 PM)

Thanks for the advice,
I live in Pennsylvania.
I had hoped to keep this nice machine for a long time, I only drove it about 20 miles before the disaster.