How to Choose the Right A/C Fitting
Jan 18, 2011 | Categories: Maintenance, Products 
Circulating the refrigerant in an air conditioning system is more complex than the plumbing required for a heater. Circulating heated antifreeze and water stresses the hoses and their connectors with around 15 psi. A fully charged and properly maintained A/C system sustains a much higher load. When the system is off it’s in the neighborhood of 65 to 125 psi. When in use, you’ll see around 275 psi on the high side and 35 to 40 psi on the low side. For that reason, greater care must be taken whenever working with hoses and fittings on an A/C system.
A heavy-duty HVAC parts catalog will have dozens of pages listing refrigerant hose fittings of different makes, sizes, and angles. To you, of course, the only one that matters is the one that needs to be replaced. Here’s what your parts distributor needs to know in order to help you make the right choice:
1. The type of fitting you need: male or female O-ring; male insert O-ring; male or female flare; male or female springlock; or pad mount.
2. The fitting size. Measure the outside diameter of the tube directly behind the nut.
3. The hose-end size of the fitting. Measure the outside diameter of the part of the fitting that will insert into the hose (this is the same as the inside diameter of the hose).
4. Is the fitting regular, step-up, or step-down?
- Regular: The hose-end size is the same as the fitting size. For example, a #6 hose-end and a #6 fitting.
- Step-up: The hose end size is larger than the fitting size. For example, a #8 hose-end and a #6 fitting.
- Step-down: The hose end size is smaller than the fitting size.
5. Is the fitting straight or angled (45 or 90 degrees)?
6. Is the connection to the hose an Aeroquip EZ Clip, Beadlock, reuseable fitting, or some other specific type?
7. Are there charge ports? Many refrigerant fittings have charge ports for checking pressures or evacuating or refilling the A/C system. They come in two types: a simple Schrader valve and a quick-disconnect valve.
To learn more about how to choose the right A/C fitting, contact your nearest Red Dot distributor.
