How to Find an AC Leak in your Car

“How to find an AC Leak in your Car.” Welcome to Mercie J Auto Care, Where Compassion and Craftsmanship Come Together. I'm Rick Smith, ASE Certified Master Technician. Automotive air conditioning refrigerant or “freon” is in a sealed system, so theoretically it will only get low if there is a leak. It is not uncommon for a small amount to leak out over a number of years from the compressor seal, so if the system is older than five years it might need a slight amount. But if we have lost a significant amount in a season, then there is a leak somewhere. There are a number of different methods to trace freon leaks in air conditioning systems. None of them are foolproof. There are very expensive electronic leak detectors. I personally don’t like them because they can often give false readings. The most common method is to put dye in the system and then look for evidence with a black light. It works great, but the system has to run long enough to lose some refrigerant. Also you cannot see the evaporator because it is in a housing under the dash. If an evaporator has a large enough leak and has been leaking for some time, you might have an odor from the vents. If the system is completely empty and the leak is large like a rock strike on the condenser or a failed ac hose, an old school method of filling the system with air pressure or refrigerant and spraying soap and water over all visible components works wonderfully also.