We have a stand-alone, wall-mounted A/C unit that exhausts to the outside and is hard-wired to a wall switch to turn the unit off and on. The unit is about 10-12 feet above the floor and the switch is about 6 feet above. Lately I have noticed that the room has gotten pretty warm, indicating that the A/C unit isn't turning on. If I turn the wall switch off and then back on again, the unit turns on and runs normally until the next time this happens (sometimes it happens on the next cycle and sometimes it doesn't happen again for a day or two - there's no obvious pattern.).

The question is, does this sound like an electrical problem with the switch (loose wire, for example) or with the unit itself? Should I call an electrician or an HVAC guy. Any troubleshooting/diagnostic tips will be greatly appreciated!