Are you having problems with your AC or heat pump unit?
If your air conditioner has stopped working this summer you may want to call one of the residential HVAC contractors in your area. I make this recommendation simply because with this summers scorching heat the last thing you want is to not have a working heating and cooling system.
Now, you can try and fix the problem yourself but if you are not a 100% sure in what you are doing you stand a high risk of actually making things much worse. If you rent a house or apartment then the best thing to do is to contact the landlord and let them deal with the problem. The only downside to this option is that they will most like take their time and hire the cheapest company they can find.
If you do decide to find an AC or heat pump company on your own the process is quite simple. All you need to really do is go online call all the companies on the first page of your search. Be sure to compare all of their recent work and then make your decision on whom you feel is the best company to work with.