Since I got my Aveo ('06 LS sedan) the A/C blower fan only worked on 1-3. Turning the knob to position 4 stopped the fan from running. I have spent a few weeks looking into it and through suggestions replaced the relay in the cabin fusebox thinking that my issue was a faulty relay. That didn't fix the issue. Today at work (O'reilly)I looked up the issue and found a circuit diagram on Mitchell 1. Apparently the circuit uses a separate feed for the high speed power to the relay that turns it on (over complicated IMO. The feed comes from a 30 amp JCASE fuse in the engine compartment fusebox (weird). So out to the parking lot, popped the hood and looked in the fusebox and there was the problem. There wasn't a fuse!?! I went back in and got a fuse, installed it and was rewarded with the high speed blowing, all functions working. All i need now is to get the AC compressor warrantied out and get the AC back working before summer hits. Hope this helps someone, because it sure baffled me.