Technician Handbook Air Conditioning for Collision Repair Gaskets & O-rings Both rigid and flexible lines connect AC components. High-pressure lines are smaller in diameter, and all joint fittings use a gasket or O-ring to help seal the system. • O-rings are made of various materials; each is selected to deal with the particular refrigerant and lubricating oil used. • Fittings are typically one of three types: - Do not reuse seals and O-rings. - Threaded tube-type – used between hoses and lines. Older vehicles equipped with CFC-12 refrigerant have threaded metric fittings. Other vehicles may use metric or SAE (inch unit) threads for CFC-12.
Fittings in an HFC-134a system are always metric and do not have notched corners on the hex nuts for identification. - Block-type – used at system components. Block fittings provide more accurate positioning of the sealing surfaces, and they reduce the risk of tearing an O-ring due to rotation during assembly. - Quick-disconnect (see next page). Tightening Fittings When tightening fittings, the correct torque is important for a proper seal. Too little torque will not provide enough pressure on the O-ring to seal and may allow the fitting to move. Too much torque may distort the fitting and make it difficult to disassemble later.
Torque specifications for the different types and sizes of fittings are described in the Vehicle Repair Manual. In order to apply the right tightening torque, the threads must be lubricated with oil. To prevent twisting and to relieve tension on rigid and flexible lines, hold one fitting stationary with an open-end or flare-nut wrench while tightening the other fitting. In the case of a threaded tube fitting, the male end should be held while tightening the female threaded nut. SERVICE TIP During inspection and estimating look for kinked, bent, dented or worn hoses and lines. Look for signs of leaks at the connections. Collision Repair & Refinish Training 15