a/c blower works on high speed only

My front a/c blower worked only on high speed for weeks. Today I took it to the dealer to get it fixed. They replaced the resistor, the relay, and the blower. The blower worked on all speeds for about an hour... now the blower doesn't work on any speed setting. Any thoughts? Why would it work for a short time? Something overcharging? Shorting? And, why can't "Mr. Goodwrench" figure out the problem?

take it back to the dealer, and tell them what happened, they will have to fix it. most of the people at dealers are a bunch of idiots, im very bitter about them all and never let them touch my vehicle.

-rob