The answer to 'tune-up not cooling' is that there could be several common causes, such as a refrigerant leak, a problem with the compressor, or issues with the air handler or ducts. Symptoms may include warm air blowing from the vents, the system running constantly, and the home not reaching the desired temperature.
Some potential solutions include checking the air filters, cleaning the condenser coils, and ensuring the refrigerant levels are correct. However, it's important to note that many HVAC issues require the expertise of a professional technician, especially if the system is older or the problem is more complex.