Having problems with my cars ac system?

I have a 1998 Honda Accord and my vents are blowing air even when all lights are off. The ac control knob is also in the off position. This usually happens at higher speeds. Will stop when I'm at a stop sign or at a red light. Is this going to be a big fix for me? Will it cause any problems for the battery? Any help will be appreciated. Thanks

Read more: Having problems with my cars ac system?