When your air conditioner blows only mildly cool air or no cool air at all, it’s probably low on refrigerant, the gas that many people still refer to as “Freon” but which now is a different substance, R-134, that’s less damaging to the environment. That means it’s probably time for an A/C recharge, but there’s more to it than just filling ’er up. Because the refrigerant operates in a closed system, the most likely cause for low levels is a leak in the air-conditioning system. The most common practice by repair shops is for a qualified technician to inspect the system for obvious leaks, such as in hoses, pipes or the air-conditioning compressor, and make repairs as necessary. Can you save money by merely topping off the system with refrigerant? Possibly. Could you even do it yourself? Yes (kits are available from parts stores). But there are a couple of major issues with that approach. There’s no way of knowing how much refrigerant is left in the system, so even a qualified technician would have to guess as to how much to add to top it off. Systems vary, but each one holds a specific amount of refrigerant. The only way to know it’s full is to evacuate the system and fill it with the specified amount. Secondly, topping off the refrigerant doesn’t fix leaks or whatever other issue caused the system to run low, so it’s only a temporary fix at best. The air conditioner might work for a while, but most systems are designed to shut down once the refrigerant falls to a certain level, and eventually you’ll be back to only warm air. Small leaks, such as pinholes in hoses, can be hard to find, so the work might not be done even after a complete evacuation and recharge. The air conditioner might stop working after a few days, and when you return to the shop they might have to inject dye into the system and trace it with a black light for leaks, which could be in a hidden location such as the A/C evaporator, which is behind the dashboard.
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