I think we covered this earlier. It doesn't matter which brand it is. Those variable speed controllers are computers. They are just as susceptible to heat, cold, dust, moisture, insects, and electrical problems, as the computer you are using to write this. Would you set your PC out on a pole in the elements? Then you should be just as careful with variable speed drive computers.
Even if you put the controller in the den with your PC, you are still going to have problems with it.
However, here is a recent link on how to solve the problems with this type system.