Q: Aircond most of the time blows cold air but "sometimes" warm

If the last inspection of the system was two years ago, it is possible for a leak to have developed since then. The only way to rule out a leak is to sweep the system with an electronic leak detector. If, and once, there are no confirmed refrigerant leaks, and the refrigerant gauge pressures, high and low side, are checked and found to be normal, intermittent blowing of warm air is commonly due to premature compressor shut down (or "short cycling"), which in turn could be due to a faulty compressor clutch or something like high head pressure that activates the high pressure cut-off switch (in turn due to a possibly blocked condenser or non functioning condenser cooling fans) or, another possibility is an internal blockage at the expansion valve in the evaporator. Trapped moisture, that intermittently freezes and thaws at the expansion valve, can also cause the symptom you are describing, particularly if the system dryer was not replaced when the system was serviced two years ago. Regardless of the exact cause of the present problem, the cause can absolutely be pinpointed and resolved if you request an air conditioning system inspection. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.