General radiator fan resister

[craighgt155]

Hi all could anyone tell me where is the best place to try and buy the resister thingy on the radiator fan. I have had to join the two wires together to get the fan to come on when engine upto temp.
What is it actually for. what is it's purpose and could i be causing any damage by connecting the two wires together.

 

[aurick86]

the Fan has 2 speeds:
1st speed has the fan and the rezistor linked in series at 12v resulting a slower speed.
2nd speed is just the fan linked to 12v thus a higher speed, for when the heat reaches a certain temperature.