control wiring diagram anyone?

can anyone sort this out for me . i cannot get my head around it 

i need a wring diagram to do the following

i have a  fan controller that operates a fan when it reaches a certain temperature ,instead of the fan i want it to operate an 12 volt 2 wire actuator

when the desired temperature is reached the power comes on and the actuator will open , when the temperature drops the power to the actuator will be cut .and  i need the actuator to  then close by having the polarity reversed and getting the power to do this from somewhere  . is this possible

i hope you can understand what i am asking and give me a solution

thanks

There is a way to do it but you need th be able to stop the action when the actuator reaches it's full extension and retraction. Micro switches are commonly used for this.

i couldn't see the wood for the trees

must have had brain freeze or something

thankyou very much

sorry for taking so long to get back to you but thought i would let you know that it works lovely