What causes your air conditioner to not blow cold air?
gas leak or wrong wiring
First determine the symptoms the air conditioner is having. For example, does it have power, is the fan running but no cold air, is the cold air not cold enough? Then you can look up possible causes on the web in sites like http://www.repairclinic.com/Air-Conditioner-Troubleshooting?red=Air-Conditioner-Repair-Help