On a car, if you wire the fan BACKWARDS, the fan will run in reverse. This happens when people by-pass the thermistor. It's not a problem, just flip the two wires going to the fan. You can test it by (carefully) holding a sheet of paper between the fan and engine and see if it blows TOWARD the ENGINE> You want it to pull air through the radiator.

You reversed the supply.Is it a single phase or 3 phase.Dc or AC? .Ascertain the input supply point.

Cars and Transportation issues ONLY. Not about FANs.

Because somebody moved the switch.