First of all you can easily clean the internal block of air conditioner by yourself, practically all modern split systems have easily removable panels, allowing to take off filters, wash them with a soapy water, dry and put them back. The main thing is not to forget to do it periodically. We often ignore the fact that an effectiveness of heat exchange directly depends on free unobstructed accessibility of air conditioning.
It is also easy to determinate if the outdoor unit is dirty or not, simply by looking at the back of the outdoor unit. If the lugs of the heat exchanger are covered with dust, it is time to clean them. Otherwise the heat dissipation will deteriorate, resulting in a decrease in heat transfer efficiency and a sharp drop in cooling or heat output of the system.
Another indication of the need to check the split system is a fall in cooling or heating capacity. In the absence of dirt on the heat exchangers, this could be an indirect indication of a more serious problem: refrigerant leakage from the line. In its turn low freon pressure can be the reason of compressor breakdown. While trying to reach a temperature mode, the compressor of a conditioner is forced to work at its full capacity, increasing the number of cycles of freon pumping through the main.
Any air conditioner as a hard home appliance requires timely servicing and maintenance, then it will work long and correctly and it is recommended to have your air conditioner serviced twice yearly.