More likely it is out of gas. Gas never get consumed even after 5 - 10 years if there is no leak. So if its low on gas or completely out of gas you need to find the leak and then repair it and then top up gas.
Once leak is repaired, gas is there and still if you get hot air that means compressor is not working or have some minor or major issue. Usually compressor fails very rarely, so dont worry it must be leak and gas issue.
all lubes and filter like engine oil and oil filter, gear oil and gear oil filter, radiator coolant, brake oil, PSF etc
Brake pads, brake drums check (or re surface them)
Check or change fuel filter and fuel line.