I assume that you used the same power cables that sent electric to the old fan. Did you insure that the fan was set up in the proper "pusher" mode before you installed it. In most cases, the fan blade needs to be removed and flipped to be used as a pusher instead of a puller. Then you have to insure that the polarity of the wires is properly observed.
I would check that the fuse is good to supply the power(usually a large fuse of 15+ AMPS) and then you may want to insure that the temperature sensor is functioning properly.