If your home air conditioning system suddenly stops working, it could be due to a number of factors. First, check to make sure that the power is turned on and that the unit is properly plugged in. If so, then the problem could be with the compressor, which may need to be replaced. Another possibility is that there is a coolant leak; if this is the case, you will need to have a professional repairman come and fix it. Finally, it could simply be that the air filter needs to be replaced. Whatever the problem may be, it is best to have a professional take a look at it in order to get your AC up and running again as soon as possible.