My A/C last summer started blowing hot air at random times. It is doing it again this summer. It only does it when I have it working on full blast. It will be blowing strong and cold for awhile and then switches to hot or outside air (I live in AZ so all air is HOT) for awhile (a minute or so) then switches to cold. What does this mean?

 

When it is not cooling, pull over and look under the hood (engine still running and A/C button pressed). Note if the condenser fan is running, and if the compressor is engaged. If you find the fan running but the compressor not engaged, you probably need to adjust the clutch gap. It could also be the compressor relay.