How Do I Recognize a Faulty Air Compressor in a Lumina?

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    • 1). Turn the air conditioning switch on. Listen to the engine speed. It should increase slightly as the compressor engages. Listen for noise coming from the compressor. If it is faulty it will make a rattle and ticking sound.

    • 2). Check the air conditioner fuse. If the fuse is good, check the air conditioner relay in the electrical panel under the hood. Swap the air conditioner relay with the horn relay to see if the relay is faulty. Do this with the engine running and the air conditioner switch in the "on" position. If the compressor does not come on, test the "low pressure" switch located in the suction line. The suction line runs from the firewall to the compressor. It is the larger of the two lines attached to the compressor. A two-wire switch with a black plug is located on this hose assembly. Unplug the switch and jumper across the connector. If the compressor comes on, the refrigerant is low. If the compressor does not turn on, test the connector with a test light and make sure there is voltage present. If not, there is faulty wiring to repair.

    • 3). Test the compressor clutch. The clutch is an electromagnet. When it is energized it pulls in the compressor drive plate. Unplug the compressor and attach jumper wires from the car battery directly to the connector. The clutch should pull forcefully in when power is applied and release when power is removed. If the clutch fails this test, replace the compressor.

    • 4). Test the compressor for major internal damage. The compressor is a pump. Testing the output pressure ability of the pump requires installing a manifold gauge. A manifold gauge can test the low-pressure side, or inlet side, as well as the high pressure, or outlet side, at the same time. Install the gauge to the high-pressure connection on the high pressure hose, which is the smaller hose attached to the compressor. Attach the low-pressure hose to the fitting on the large compressor hose assembly. The high-pressure reading should be close to 200 pounds of pressure while the low-pressure side should read close to 40 pounds of pressure.

    • 5). Leak test the compressor connector fittings when the system is fully charged with refrigerant. The compressor hose assembly is installed with sealing rings to ensure there are no leaks. Although these seals rarely fail, spray soapy water over the fittings and look for bubbles. If there are no bubbles, the seals are good.

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