Refrigerant Service Ports

 More than meets the eye


Collar dimensions are set by SAE Standards for low-side and high-side service ports. Note the knurled base on the low-side port (left).

photo: MACS


Viewed from the bottom: the high flow-rate port (center) is installed as a complete assembly. Note the saddle mount on the M-10 port (left).

photo: MACS

by Jacques Gordon

Refrigerant service port fittings perform the function of a simple check valve, but they must meet several different demands that make their design quite complex. First of all, they must conform to SAE Standards that define the fitting diameter, locking collar dimensions and distance from the opening to the tip of the valve stem on both the high- and low-side fittings. The goal is to make sure that only the correct service equipment coupling (R/R/R machines) can be connected to them.

Everything below the valve stem tip is designed primarily to satisfy different needs of the car manufacturer. For instance, on the GM assembly line, it takes less than one minute to evacuate the A/C system to 29.45 inHg, pause for a leak-check, then fill it with refrigerant and oil. Of course the vacuum pumps and filling equipment used on the production line are far more powerful than the equipment in a repair shop, but the design of the service port also influences the speed of the operation. Since port diameter is already set by the SAE specification, the valve core must be designed to provide a high flow rate on large systems that require more refrigerant. Schrader makes a service port fitting that flows particularly fast, but it must be installed on the vehicle as a complete assembly. Normally the metal body of a service port is brazed to the metal refrigerant line and then the valve core and rubber seals are installed after it cools. To install a fully-assembled service port, a female-threaded collar is brazed to the metal refrigerant line first, then the service port is screwed into place and sealed with an O-ring.

A less expensive high-flow port uses a ‘saddle’ mount to locate the body on the metal refrigerant line. After it’s brazed into place, the body is used as a pilot to locate the hole that is drilled into the line, and finally the valve core is installed. On a standard service port, the body has a knurled collar at the base that fits directly into a hole in the metal refrigerant line, and the valve core is installed after brazing.

To make it easier to design a quick-disconnect fitting, the threads for the cap are inside the service port body. This also minimizes the possibility of damage that would prevent the cap from screwing on tight enough to make a positive seal. The cap really isn’t designed to hold system pressure, but it must protect the valve from contamination. Tighter regulations on system leakage make the service port cap a more critical part than ever.

Our thanks to Schrader International for contributing parts and information for this article.

The Mobile Air Conditioning Society’s blog has been honored as the best business to business blog in the Automotive Aftermarket by the Automotive Communications Awards and the Car Care Council Women’s Board!

When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.

If you’re a service professional and not a MACS member yet, you should be, for more information.

You can E-mail us at . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here  to find out more about your car’s mobile A/C and engine cooling system.

The 34th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Power Up  will take place January 16-18 2014 at the Sheraton New Orleans.


About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues.
This entry was posted in #1234yf, Mobile Air Conditioning, Refrigerants and tagged , , , , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s