Attaching the Gauge Manifold Set

By 20 April 2015

Now that you know how to read the gauges and how to correct for variations in vacuum and pressure caused by different altitudes, you’re ready to hook them up. Pay close attention and you’ll learn how to do it right. Every time you need to diagnose a problem in the air conditioning system, you are going to have to examine the system’s overall performance, particularly system pressures and refrigerant flow. These performance parameters can only be checked with the manifold gauge set.

In theory, hooking up a set of gauges is simplicity itself:

1 The low side hose (usually blue) is attached between the low side gauge and the low side of the system.
2 The high side hose (usually red) is attached between the high side gauge and the high side of the system.
3 The service hose (usually yellow, sometimes white) is attached between the service (center) fitting on the manifold and either a vacuum device or refrigerant supply, depending on what you intend to do to the system.

In reality, hooking up the test gauges isn’t always this simple, because the high and low side service valves differ somewhat – in size, configuration and ease of access – from system to system. So don’t be surprised if you buy or borrow a gauge set only to find that it doesn’t hook up as easily as you had hoped. Fortunately, there are service adapter fittings available for every conceivable purpose.