Fix an AC leak in your car

Learn the most common locations for an AC leak in your car

Auto air conditioning (AC) systems can develop leaks in several common areas. Identifying the leak location is crucial for effective repairs. If your car is losing AC refrigerant, add fluorescent dye to the system. Then drive it for a while and use a black light to locate the leak.

The most common car AC leak locations

• Hoses and Connections— Rubber Hoses: The rubber hoses that carry refrigerant can develop cracks or splits over time, leading to leaks. To disassemble a joint, you first have to have

Ac connector with neoprene O-rings.

to evacuate the system. Once the system is empty, you’ll most likely need a special disassembly tool. After the joint release mechanism is activated, you may need to heat the joint with a heat gun to warm the components. Do not get them red hot, just warm.

Replace the O-ring with new parts and coat the new rings with the specific refrigerant oil recommended by the manufacturer. Most AC leaks are caused by deteriorating “O” ring seals. Every joint in the system has at least one O-ring seal. These O-rings are specially designed to be compatible with refrigerant and AC oil. You MUST replace them with the specific type of O-ring for your vehicle. You cannot use black plumbing-style O-rings. Most older vehicles came with neoprene O-rings, but green HNBR o-rings are the preferred style. To learn more about HNBR O-rings, see this post. Then, reassemble the joint.

Find a complete O-ring kit for your vehicle. It’ll have all the right sizes for your system

• Condenser—The condenser is in front of the radiator, exposing it to roads, salt, and bugs. Over time, road salt can eat away at the aluminum, resulting in a leak. Stones and rocks can also kick up from the road and damage the condenser tubing.

This image shows typical rock damage to an auto AC condenser

• AC Compressor— AC compressor leaks in two places: the compressor shaft seal or a body seal. A compressor shaft seal leak is the most common

This is a typical AC compressor shaft seal. It’s a two-piece unit with a ceramic sealing face.

and easiest to diagnose. When the shaft seal fails, refrigerant oil leaks out of the compressor shaft seal onto the compressor pulley and is flung around the underhood area in a circular pattern.

It’s far less common for a car AC compressor to develop body leaks. However, if you see oily spots on the compressor body, check those areas for dye accumulation.

• Service Ports— The service ports (low and high side) used for recharging the refrigerant can leak if their Schrader valves are damaged or not sealed properly. You can replace the valve core without evacuating the system. But you’ll need a special valve core removal tool. See this post to learn more about replacing a leaking Schrader Valve Core Leak.

• Receiver/Drier or Accumulator— These components are exposed to the elements and can develop leaks at their fittings or develop corrosion and pinhole leaks.

• Evaporator— Located inside the dashboard, the evaporator core can develop leaks, often due to corrosion from moisture and contaminants. Replacing an evaporator core requires the complete removal of the dash, so make sure the shop is positive the leak is coming from the evaporator before agreeing to this repair.

• Pressure Switches and Sensors— Pressure switches and sensors that are threaded into the AC system can develop leaks at their connection points.

Never use AC sealer to stop an AC leak

AC sealers never work on leaking AC hoses, O-ring seals, compressor shaft seals, or rubber hoses. Worse yet, if you ever plan to take your car to a shop for professional AC repair, an AC system with leak sealer is considered a contaminated system. The sealer damages the shop’s refrigerant recovery machines. So you’ll be charged extra to remove the contained refrigerant.

©. 2012 Rick Muscoplat