How to Hook Up an A/C Manifold Gauge
Automotive air conditioning works on the physical principle known as the Second Law of Thermodynamics: Gas cools on expansion. For the system to work properly, it must contain the proper charge of gas otherwise known as refrigerant or R-134a, the most common compound used in cars. Technicians use a tool known as a manifold gauge set to check the system and monitor the pressure as they add freon when servicing or troubleshooting air conditioning. Once an expensive piece of equipment, manifold gauge sets are now widely available at reasonable prices and can save hundreds of dollars in maintenance costs.
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Things You'll Need
- A/C manifold gauge set
- Clean rags or shop towels
- Basic automotive tool set
Instructions
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Open the engine compartment and look for the air conditioning components. The compressor will be a belt driven device inline with the water pump and power steering. Identify the air conditioning compressor by the two metal and rubber lines with vertical connection fittings leading to and from the unit. The caps on the fittings are often red and blue to correspond with the hoses on the gauge set, but they may also be other colors. Note that one hose is larger in diameter than the other. The larger hose is the low pressure connection for the blue hose.
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Remove the blue, or low pressure cap, and connect the blue hose from the gauge manifold to the fitting. The connector has a sliding collar and a knurled knob. Slide the collar up and place the connector over the fitting and tighten the knurled knob with your fingers only. Repeat the procedure for the red, high pressure, hose.
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Connect the yellow hose, in the same manner, to suit your purpose. If you are adding refrigerant to the system, connect it to the supply tank. If you are evacuating the system, connect it to the vacuum device. If you are just checking the system, leave it connected to its holder on the gauge manifold set.
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