I'd be looking at the actual switch on the dash.LOL!!
We know mtr works, sounds like contacts may be dropping out??

 

But my explanation is much more complicated, involves many more assumptions, and is much less likely to happen.

That's why I posted it..

The fan itself works on all settings which is why I figured the switch itself is probably good. At least that's how I read the post. The AC on off function is all through that AC button..

 

Agree Derf, AC button may be root cause

 

But why would the AC switch only have an intermittent connection in positions two and three of the fan switch? I believe the fan runs in all positions

 

I had a similar issue with my Kia Forte and it was the connector to the blower motor. Sum beech had melted and had a short in it. I spliced in a new one and haven't had any problems since.

 

Ha, I have same issue on 05 I just got. Ac and fan work at 1-2. But ac light goes off at 3-4. But fan works at all speeds. I’m going to try a new blower module resister first.
hvac control assy? Perhaps.
weak alternator? Hmm, I suppose it could be part of issue.

 

Resistor pack controls current to blower motor for each speed except high.

You stated all fan speeds function.
Therefore resistor pack is working as designed.

 

Try hooking up jumper cables to another battery with both cars running.

If it is a weak alternator and battery issue, the addition of another current source, the other car's battery,+ alternator should provide more than enough current to the system in your vehicle. Make sure they are beefy (low wire gauge number) so that The resistance of the jumper cables does not significantly limit the current flow

A jump box should work as long as the terminals are live. Some of them you need to push a button to make the terminals live.

 

Has other issues also. I fixed them and sold it. I never got around to changing resistor as test. Or inspecting fan wire harness. Ironically my reply is same as someone who did not have issue. I did not investigate or try to fix it. I’m just a person who also had same issue.

 

I had this exact same problem on my Vue, 2006 base w/V6 . The solution was replacing the blower motor resistor, GM part # 15-80546. It's located on the passenger side, right under the dashboard, and was a pretty easy swap to the new one (it's only 2 screws if I recall).