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Easy Diagnosis of Ac Failure on 98 Gmc Yukon

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Driving around on a hot day in a car without a working air conditioner can be uncomfortable and even dangerous in extreme heat. Diagnosing the reason that your air conditioning isn't working will help you determine whether the problem is one that you can fix yourself or if you need to take it to a repair shop. You are also less likely to be taken advantage of at a repair shop if you already know why your AC is not working.

  1. 1

    Turn the air conditioning on while the car is running. The air conditioner won't run properly unless your engine is running. The best setting for diagnosis is "fresh air" (not recirculated) with the air blowing out of the center vents in the dash and the AC turned on.

    • Start with the fan speed turned to its highest setting.
    • If your car has a "Max AC" setting, select that option.

  2. 2

    Listen for unusual noises coming from the AC. Noise could indicate that there is a problem with your compressor and that it needs repair or replacing.

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  3. 3

    Feel the air coming out of the vents. You will need to know if the air is cold, room temperature, or hotter than the air around it. Also note if it starts cold but turns warmer, or if it is usually warm but blows cold intermittently.

  4. 4

    Notice the air pressure. Turn the air pressure to the high and low settings and see if the airflow changes like it normally does.

  5. 5

    Smell the air coming from the vents. If there are unusual smells, you could have a leak. You may also need to change your cabin air filter.[1]

  6. 6

    Inspect your car's fuses. Check your owner's manual for the location of your car's fuse panel, as it may be under the hood, in the trunk, or even in the driver's foot well area. A blown fuse can cause your AC to stop working.[2]

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  1. 1

    Check all of the vents. Be sure that air pressure is coming out of the vents that you have selected. Move the vent selector to see if the air moves to the proper vents.

    • If changing the selected vent does not alter the flow of air, you likely have a blend door problem, which will require replacing the doors inside the dash that determine the direction of the air flow.[3] [4]
    • Blend doors change position when the temperature selection is changed, blocking the flow or permitting the flow of either hot or cold air.
    • Sometimes an AC system with a mode door problem could be working fine, but the air flow is being directed somewhere else, like back out to the engine, instead of into the car.

  2. 2

    Look at your cabin air filter. Especially if the air coming from your vents smells funny or if you think you have had a slow decrease in pressure for some time, check the air filter. You will be able to see if it has a buildup of dirt or debris on it.

    • It is possible that your cabin air filter is so blocked that it is interfering with your air pressure, and replacing it will be a relatively easy an inexpensive fix to your problem.
    • Your car manual may have instructions on replacing the cabin filter. If it doesn't, try searching online for "replace cabin air filter" followed by the year, make, and model of your car (for example, you might search for "replace cabin air filter for 2006 Toyota Camry").

  3. 3

    Check for a blower motor problem. The easiest way to do this is to try turning on your heat. If you have weak air flow when the heat is on as well, your blower motor may have gone out.[5]

    • A blower motor may have a resistor problem if your air only blows on the high setting but will not blow on a lower setting.
    • Unfortunately, mice and other rodents sometimes build homes in car HVAC hoses and can get caught in the blower motor when the car is started. A loud noise (or bad smell) coming when the heat or air are running could be a sign of this problem.

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  1. 1

    Find the front of your AC condenser. It is normally located in front of your radiator. If there are leaves or other dirt or buildup blocking it, remove them and clean the area.

  2. 2

    Look under the hood at the AC compressor clutch. If your air pressure is normal but the air is hot, you may have a compressor problem. Checking to see if the compressor clutch is engaging is a simple visual inspection.[6] The compressor is usually located towards the front of your engine, just inside the grill of your car.

    • Your car should be running with the AC on to check the compressor clutch.
    • The compressor looks like a small motor with a large wheel on the end. The wheel (which is the compressor clutch) should be spinning. If it is not spinning, you have a problem with your compressor.[7]

  3. 3

    Check the tension on the belt of the compressor. It should be tight. If it is loose, you need a new compressor belt.[8]

  4. 4

    Find any coolant system leaks. One of the most common AC temperature problems is low refrigerant. The AC system is closed, so refrigerant should not be lost unless there is a leak.[9]

    • Look for oily residue on or around hoses that attach AC components together. Oily spots may indicate a refrigerant leak.
    • You may consider using an electronic leak detector, which can detect much smaller quantities of refrigerant.
    • There are also some testers that use dye, UV light, and protective glasses to find leaks.
    • If you do find a leak, you will likely need to hire a professional to repair the leak. You will probably need new parts too, as many of the components cannot be repaired or patched.

  5. 5

    Check for freezing. If your AC blows cold initially but then stops being cold after some use, it could be freezing. Excess air and moisture in the system may lead components to freeze (literally).[10]

    • Freezing can also be caused by an oversaturated receiver/drier or accumulator.
    • Turning the system off for a while and letting it thaw will temporarily solve the problem.
    • If the problem is persistent, you may need your system to be flushed or evacuated with a vacuum pump.

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Add New Question

  • Question

    Can a bad temp sensor cause AC not to work?

    Ed Beery

    Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

    Ed Beery

    Automotive Specialist

    Expert Answer

    Definitely! If the temperature sensor does not send a signal, then the AC will not turn on. Just keep in mind that these sensors are located deep in your HVAC system behind the dashboard, and can be difficult to inspect and replace.

  • Question

    How do you test a blend door?

    Ed Beery

    Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

    Ed Beery

    Automotive Specialist

    Expert Answer

    Start your vehicle and turn on the AC with the fan on high. Then, cycle through the selector options on your HVAC control, feeling for cold air from each position. Positions that don't blow cold air may have a temperature sensor issue, while positions that don't blow any air might have a blend door actuator problem.

  • Question

    How do I know if my AC fan is bad?

    Ed Beery

    Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

    Ed Beery

    Automotive Specialist

    Expert Answer

    Your AC fan will either have inconsistent air movement or no air movement at all.

  • Question

    How do I know if my pulley is bad?

    Ed Beery

    Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

    Ed Beery

    Automotive Specialist

    Expert Answer

    The pulley either doesn't turn or turns inconsistently when the AC clutch engages.

  • Question

    What happens when an AC belt goes bad?

    Ed Beery

    Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

    Ed Beery

    Automotive Specialist

    Expert Answer

    You might notice a high-pitched squeal or chirp from the belt when the AC is turned on. There might also be intermittent cooling in the system as the belt gains and loses traction.

  • Question

    How do I know if my AC clutch is bad?

    Ed Beery

    Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

    Ed Beery

    Automotive Specialist

    Expert Answer

    The tell-tale signs of a bad AC clutch are the clutch not engaging when the AC is turned on (and voltage is present); the clutch clicking or banging but not engaging when the AC is turned on; the clutch slipping in and out of gear when the AC is turned on; and/or the vehicle idle dropping noticeably when the AC is turned on.

  • Question

    How do you know if your car AC is low on gas?

    Ed Beery

    Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

    Ed Beery

    Automotive Specialist

    Expert Answer

    Low or no gas might be the problem if air is flowing throughout the system when the AC is turned on; the air is not cold or cool and doesn't get cold or cool anywhere in the system; the AC compressor is turning; the AC clutch is not making noise; and the AC clutch engages when the AC is turned on.

  • Question

    Can a blown fuse box cause your AC not to work?

    Community Answer

    Sure, if the fuse that feeds your AC compressor or relays is blown and not delivering +12VDC you will have no AC.

  • Question

    What do I do if my A/C isn't blowing air?

    Community Answer

    Possibly either a fuse or the blower motor isn't working. Check the fuses under the hood, and check under your glove compartment for a cylinder shaped motor. With the A/C on, gently wiggle the cord to test for a short in the adapter. If this doesn't work, then you can use a fuse tester to see if your blower motor is getting power.

  • Question

    My truck heat works; it defrosts, but only on 3 and 4. It only blows hot air on 3 and 4. I've put coolant in it, and it works for a few seconds, then stops. I checked for leaks, and it doesn't have any. What can I try next?

    Community Answer

    A blower motor may have a resistor problem if your air only blows on the high setting but will not blow on a lower setting.

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  • Do not add refrigerant unless you are sure that low refrigerant is the cause of the problem because overfilling the system with too much refrigerant can cause severe damage.

  • It is always best to consult a professional to do repairs to your vehicle.

  • Wear safety glasses and work in an open environment, where fumes won't overwhelm you. Never touch your eyes or mouth after handling Freon or other chemicals. Wear long sleeves and gloves whenever possible.[11]

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About This Article

Article Summary X

To diagnose why the air conditioning in your car isn't working, start by turning your car on and setting the AC to full blast. If strange noises are coming from the AC, there could be an issue with the compressor and it may need to be fixed or replaced. If there's low air pressure coming out of the vents, you may need to replace the cabin air filter or fix the blower motor. If the air coming out is warm, the coolant could be leaking or you may need to clean the AC condenser. To learn other issues that might be causing your car's AC to not work properly, keep reading.

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Source: https://www.wikihow.com/Diagnose-a-Non-Working-Air-Conditioning-in-a-Car

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