There are several reasons behind your air conditioning is not working or fail to provide proper cooling, such as the presence of faulty compressor. Apart from that, there are several other reasons too that might affect the proper functioning of your residential AC Unit;
Your AC unit air filter might be clogged or dirty.
It might be due to improper working of fan or fan motor of your AC.
Dirty condenser coil
Very high temperature
An undersized air-conditioner
If above-mentioned things working fine then you should contact ac repair services near you to resolve the issue.