Your car’s AC (air conditioning) system usually squeals due to a worn or slipping serpentine belt. This belt drives car accessories, like the AC compressor and power steering pump. If the belt cracks, it can slip, producing a loud squealing noise. A non-engaging AC clutch or faulty bearings can also cause this unusual sound.
Here’s a list of the most common causes:
- Worn or loose serpentine belt
- Damaged AC belt
- Faulty AC compressor clutch
- Failing blower motor or fan
- Low refrigerant levels
- Contaminated pulley bearings
What to do:
- Listen carefully: Check whether your car squeals when the AC turns on or continues to squeal while it’s running.
- Inspect the serpentine and AC belt: Look for signs of glazing or wear, and replace them if needed.
- Check the belt tension: Find the midpoint between the two pulleys and move the serpentine and AC belt with your thumb and index finger to check for proper tension. They should have 1/2 inch of play — if it’s less or more than 1/2 inch, the belts will need adjustment.
- Test the AC clutch’s coil and connections: Disconnect the electrical connection close to the coil and test it for resistance. It should have a reading between 2 and 5 ohms; otherwise, the coil and clutch will require further inspection.
- Check the refrigerant level: Use a refrigerant gauge to verify that,
- The low-pressure port reading is around 25 to 45 pounds per square inch (psi)
- The high-pressure port reading is approximately between 250 and 400 psi. If not, you’ll have to add more refrigerant.
- Examine the idler and tensioner pulley bearings: Access each pulley to check whether their bearings are dry or have contaminated seals.
- Assess the blower motor and fan: Look for twigs, leaves, or other substances obstructing the blades. Also, check for faulty motor bearings that will need replacement.
- Consider professional help: Unlike other repairs, a DIY fix may not resolve AC problems due to their complexity, so contact professionals from AutoNation Mobile Service. They can inspect the AC components and make repairs as necessary.
But if you’re simply curious about car AC sounds, this guide will discuss them in detail and explore ways to prevent them.
This Article Contains:
- Why Is My AC Squealing in My Car and How Do I Fix It?
- What Strange Noises Can a Failing Car Air Conditioner Emit?
- 5 Surefire Ways to Prevent Noises From a Car’s AC System
- 3 FAQs on Car AC and Unusual Noise
Why Is My AC Squealing in My Car and How Do I Fix It?
Here are the common causes of a squealing AC:
1. Cracked or Worn Serpentine Belt
The serpentine belt (or drive belt) is a single belt that drives engine accessories like the AC compressor in modern cars.
Over time, this belt can accumulate dirt or glaze due to heat. Once compromised, it can slip off the compressor pulley, creating a loud squealing noise during AC operation.
How to fix it: If the serpentine belt is dirty, have a mechanic clean it. However, they’ll install a brand-new belt if it’s cracked or worn.
2. Damaged AC Belt
In older vehicles, instead of the serpentine belt, a separate AC belt drives the compressor pulley.
However, regular usage can over-stretch or glaze the belt, leading to squealing and poor AC performance.
How to fix it: If the belt is slipping, a professional will tighten it. A complete replacement is the best solution if it has exceeded its lifespan or is beyond repair.
3. Failing Compressor Clutch
The AC compressor clutch engages and disengages to run the compressor. If it has loose electrical connections or a faulty coil, it may not engage the compressor properly, creating a squealing sound.
How to fix it: A technician will test the clutch coil or electrical connections, look for rust accumulation, and replace the faulty parts.
4. Insufficient Refrigerant
Refrigerant is vital for producing cold air for the cabin. But if your system runs low on refrigerant due to an unexpected leak, your vents will blow warm air.
A lack of refrigerant also forces parts like the compressor and evaporator to overcompensate, resulting in premature wear and squealing sounds during their operation.
How to fix it: The expert will check system pressure, add refrigerant if needed, and inspect for leaks. If they find a leak, components like the AC hose will require replacement.
5. Worn Pulley Bearings
Although the drive belt powers the power steering pump and compressor, it relies on idler and tensioner pulleys for alignment and proper tension.
However, these pulleys will function correctly only if their internal bearings are well-lubricated and have intact seals. If not, they can cause the belt to slip or create friction, leading to rattling or squealing noises during AC operation.
How to fix it: The mechanic will identify which pulley is failing, the idler or tensioner pulley, and inspect its bearings. If the pulley bearings are dry, they’ll apply a suitable lubricant. But if the seals are damaged, they’ll replace the pulley entirely.
6. Faulty Blower Motor or Fan
The blower motor and fan circulate cold air in the cabin. With time, debris can accumulate between the fan’s blades, causing squealing or whining sounds.
In addition to the blades, worn or contaminated bearings inside the blower motor can also contribute to a squealing sound.
How to fix it: The technician will inspect the motor and fan blades for obstructions or damage. If internal bearings are worn, they’ll replace the entire blower motor assembly.
What if you hear sounds other than squealing?
Can your car’s AC cause those, too? Let’s find out.
What Strange Noises Can a Failing Car Air Conditioner Emit?
Some other odd AC sounds you should be vigilant about include:
- Clicking noise: A faulty blend door actuator often causes this unusual sound to come from under the dashboard. The actuator controls airflow direction and regulates cabin temperature by moving the internal panel (blend door). If the actuator’s gear (a worm gear) becomes damaged, you’ll hear a repetitive clicking noise whenever the motor tries to move the blend door.
- Knocking or rattling sound: A loose blower motor housing bracket or debris inside the AC unit can create this sound.
- Gurgling or bubbling noise: You may hear gurgling or bubbling sounds when there’s low refrigerant or an obstruction in the fluid flow. Air pockets or a clogged evaporator drain can cause this obstruction.
- Buzzing noise: A buzzing noise may indicate excess refrigerant (overcharging) in the AC system, which can strain the compressor and lead to inconsistent cooling.
- Whistling or hissing noise: Restricted airflow, resulting from debris in the vents, a clogged cabin air filter, or a partially blocked evaporator core, can create whistling or hissing noise.
Since several car parts can potentially generate odd noises, let’s see if you can prevent them altogether.
5 Surefire Ways to Prevent Noises From a Car’s AC System
To avoid driving with a noisy AC unit, you should:
- Recharge your car’s air conditioning system every one to five years or before significant seasonal changes.
- Replace glazed belts, clogged filters, and worn pulleys as soon as you notice signs of malfunction.
- Clean the vents and cabin filter to prevent debris accumulation in the system.
- Book a drive belt replacement every 90,000 miles to ensure an intact belt drives the engine accessories.
- Check the belt tension every three to six months.
Want to know more about ACs and odd sounds before fixing them?
Keep scrolling!
3 FAQs on Car AC and Unusual Noise
Have a look at some common questions people ask about weird sounds from ACs:
1. Does a Squealing AC Affect Your Vehicle Performance?
A squealing AC with poor cooling won’t affect your driving. But if you also notice battery or power steering troubles, it’s a sign that the serpentine belt is failing and needs urgent attention.
Moreover, straining components like the AC compressor and water pump can cause AC failure or overheating, which are expensive to fix.
To avoid such extensive damage, consult a mechanic when you hear weird AC sounds.
2. How Much Does It Cost to Fix a Noisy AC?
From replacing a faulty compressor to fixing a refrigerant leak, let’s check out how much this auto repair service will set you back:
- Cabin filter cleaning: $20 to $85
- Cabin filter replacement: $50 to $100
- AC belt replacement: $75 to $280
- Serpentine belt replacement: $90 to $250
- Refrigerant leak repair: $100 to $800
- AC hose repair: $150 to $400
- Pulley bearing replacement: $155 to $220
- Idler pulley replacement: $160 to $270
- Tensioner pulley replacement: $160 to $190
- AC recharge: $230 to $290
- Blower motor replacement: $300 to $350
- AC clutch replacement: $590 to $650
- Evaporator replacement: $700 to $1,300
- Failing compressor repair: $900 to $1,100
3. How Often Should a Car Owner Schedule AC Maintenance?
You should book an auto repair service for your car’s air conditioning system once a year, depending on the local weather and your usage.
Regions with extreme heat or humidity may require more frequent maintenance to keep the system running efficiently. Likewise, if you often drive in dusty or polluted environments, components like the cabin filter and evaporator may need more routine inspection.
Enjoy Quieter, Cooler Rides with AutoNation Mobile Service
Driving a car with a squealing AC isn’t just annoying; it indicates problems that need more than a simple DIY fix.
Want the squealing to stop, but don’t know where to begin?
AutoNation Mobile Service mechanics can take care of it.
Our mobile mechanics can come to you to check your AC unit and ensure you drive a cool, quiet car. We’re available seven days a week and provide upfront pricing with a 12-month, 12,000-mile warranty.
Schedule your appointment, and our experts will fix your AC troubles right from your driveway.