What Causes an AC Compressor to Make a Whining Noise When Accelerating?

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An AC compressor plays one of the most important roles in your HVAC system—compressing refrigerant into a gaseous vapor that allows the heat it absorbs to be released outside. You shouldn’t hear much from the compressor. However, banging, clanking, humming, buzzing, or hissing can signal a very significant problem. If there’s an AC compressor whining noise when it’s accelerating, this is one of the most concerning noises it can make.

What an AC Compressor Whining Noise Means

Loud whining sounds from a compressor often mean there’s an internal pressure problem. If enough pressure is released from the compressor, it might sound more like a loud scream. This shouldn’t last for more than 10 to 15 seconds. Otherwise, pressure is likely building to unsafe levels. Your AC
unit may also turn on and off frequently.

It’s a bad idea to keep running your AC at this point. Shut it off if the safety switch hasn’t done so already. Allowing the system to run can lead to more significant damage and even complete compressor failure.

The pressure that causes AC compressor whining can be due to a:

  • Refrigerant overcharge, which strains the compressor’s piston cylinders.
  • Blocked suction line, which can also cause the system to overheat.
  • Dirty coil, in which dust, grime, and mineral scale prevent heat transfer, increasing pressure and temperature until the compressor overheats and fails.

Causes of a Whining Noise When Accelerating Your Car

A bad AC compressor in a car can also make a whining sound when the vehicle accelerates. It is attached by a belt to the crankshaft. As a compressor under pressure powers up, it will make more noise. However, whining sounds when accelerating your vehicle can also be indicative of a transmission fluid leak, worn out gears, low power steering fluid, or a water pump or alternator bearing problem. If your car makes a whining noise when idling, there may be an oil leak or stuck valve.

If your car is whining, first check fluid levels and top off any fluids if necessary. Perhaps a belt needs to be tightened or replaced. When you have any doubts as to the nature of or solution to a problem, take your vehicle to a mechanic for an inspection.

Whining Noises and Your HVAC Compressor

High suction pressure is a common problem that can affect residential and commercial AC compressors. If it occurs along with low head pressure, there may be a faulty or leaky compressor valve. Signs of a bad valve include a higher discharge temperature and reduced amp draw. Low head pressure is a result of the discharge valve not sealing properly.

A worn compressor piston ring can allow discharge gases to leak, reducing head pressure and elevating suction pressure. That’s why worn rings can be mistaken for leaky valves. Another possible cause of high pressure is a leaky oil separator. Controlling the high and low sides of the system, the oil separator allows oil to travel from it to the crankcase of the compressor. Pressure rises to abnormally high levels when the needle valve gets partially stuck open, facing into the crankcase; a sign of trouble is if the oil return line is hotter than the ambient temperature.

Contact Hays Heating, Cooling & Plumbing

When you hear unusual noises from your air conditioner and/or it’s not providing enough cooling, short cycles, runs continuously, or doesn’t turn on, our trained technicians can promptly address the problem. Our AC repair technicians are fully licensed. If you have questions, such as “what causes an AC compressor whining noise when it’s accelerating?”, or about anything regarding your HVAC system, don’t hesitate to reach out to us. Call 602-362-8261 or schedule service or an estimate today.