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7 Car Air Conditioning Problems Not Caused by the AC System

Most Parma residents understand the importance of fixing car air conditioning problems to ensure comfortable driving during the hot summer months. But a working air conditioning system is also critical during the cold winter months. Even more important is being aware that AC problems can be caused by systems on your vehicle that aren’t considered part of the air conditioning system.

To save auto owners money on AC system repairs, repair shop mechanics need to start by checking these basics when diagnosing air conditioning problems. This helps to make sure the root cause of the problem is not missed and customers only pay for necessary repairs

Automotive systems that can cause air conditioning problems

At AutoTranz Transmissions, our ASE certified air conditioning technicians check non-AC related fundamentals when diagnosing symptoms that are suspicious for problems with expensive air conditioning components. Some car air conditioning complaints may actually be caused by problems that air conditioning system repairs won’t resolve.

Here are some examples of complaints that sound like car air conditioning problems but can be caused by problems with components in other vehicle systems:
• My air conditioning isn’t as cold as it was last summer.
• Dash vents don’t seem to blow as much cool air
• The temperature gauge reads higher than usual
• I don’t hear the electric cooling fan running like it used to on hot days
• There is a squealing noise when I turn on the air conditioning
• There are bad smells when I use my AC system on long drives

Below are seven non-AC problems that can affect your air conditioning system efficiency and result in complaints like those above. Included is information about the repair shop fix that will correct them.

Cabin Air Filter Service1. Cabin Air Filter Restrictions Reduce Dash Vent Air Flow

Many auto owners don’t know their vehicle has a cabin air filter. The addition of the cabin filter in recent years is a nice enhancement for drivers and passengers with allergies or other air sensitivities. It provides extra filtering of the outside air that comes in through your vehicle’s dash vents. Good filters can even reduce outside smells.

When this maintenance item is delayed or skipped, the filter can become clogged. Over time, the flow of air from the dash vents is decreased when the AC system is on. Complaints of a car air conditioning problem surface as reduced air flow from the dash vents fails to cool the inside of the car enough for comfort during driving.

Replacing the cabin air filter restores adequate airflow and the problem is fixed with cost savings to the auto owner.

2. Electric Cooling Fan Not Moving Enough Air

Most front-wheel drive cars and many SUVs and trucks now have electric cooling fans replacing the belt driven fans on older model rear-wheel drive vehicles. There can be a pair of two electric fans or a single fan that operates at two speeds. When pulling heavy loads or seasonal heat raises engine coolant temperatures, the cooling fan turns on or switches to a faster speed to draw additional airflow across the radiator and air-conditioning condenser. This also happens when the AC is turned on.

When the cooling fan(s) fail to function, the air conditioning system can’t do its job efficiently. A mechanic or electronics technician must diagnose and repair the problem, which could be caused by a bad fan relay, a blown fuse, a bad fan motor, or an electronic problem within the computer that controls these relays.

Repair of the offending electronics can restore the cooling fan(s) to proper operation and silences the complaint of car air conditioning problems.

Serpentine Belt Slipping3. Slipping belts decrease efficiency

A slipping belt affects an AC system by failing to turn the air conditioning compressor consistently, which can decrease its cooling efficiency. Worn belts can slip and fail to grab the pulley tightly or stretch and interfere with the automatic tensioner adjusting to correct belt tension so slipping is avoided. Installing the wrong sized belt will also result in slipping.

Whatever the cause is, the correct fix is to install a quality serpentine belt or v-belt that grips the pulley tightly to stop the slipping. This fix can also eliminate the complaint of squealing when the AC is turned on.

4. Radiator or AC Condenser Blocked by Leaves, Dirt, or Other Debris

When a radiator or AC condenser becomes blocked by dried vegetation, dirt, or other road debris, airflow is reduced and overheating or undercooling can happen. This is a common condition in Idaho where there is an abundance of organic matter and other wind blown debris from farming, ranching, and unimproved roadways.

Eliminating this complaint can be an easy fix. Removing the top mount from the radiator allows it to be eased away from the AC condenser so an air hose or, better yet, a garden hose can flush out the debris between them and clean the fins in the radiator and condenser.

5. Engine Overheating From Cooling System Problems

A cooling system is the radiator and coolant it circulates around the engine to transfer heat away from an engine that is running too hot. When this system fails, heat accumulates in the engine and reduces the cooling ability of the AC system. There can be many causes for coolant failing to circulate,
• A thermostat stuck in a closed position
• Internal radiator tubing plugged with sludge or debris
• Cracks in the plastic radiator tanks that leak coolant

Repairing or replacing a failed radiator or thermostat eliminates the overheating condition and allows the AC to function as it is designed.

Winter Driving SUV6. Persistent Window Fogging During Winter Driving

This problem is not caused by a malfunction. It usually is caused when a driver runs the heater on recirculation in cold, damp conditions. Moisture from breathing, damp clothes, or humidity inside the vehicle is re-circulated within the vehicle cabin and contributes to window fogging.

Since one of the main functions of the air conditioning system is to remove moisture from the air, turning on the AC system can help remove moisture from the cabin of your vehicle. Reduced fogging would also happen if recirculation is turned off allowing dryer outside air to enter the cabin. The best option would be to turn on the defrosters. That automatically turns on the AC compressor and dries the air moving into the cab.

7. Bad Air Smells When Using the Air-conditioning System

Like window fogging, a musty or damp sock smell is caused by bacteria growth on the air conditioning evaporator under the dash. When your car is driven with the AC in recirculation for extended periods, or with a low fan speed, the bacteria that thrive in moist environments overgrow and noticeable odor is increased.

There are several things you can do to combat this condition without having to pay an air conditioning technician to kill the bacteria. First, limit use of recirculation to extremely hot conditions. Second, when recirculation is on, be sure to have medium to high fan speed on. Increased airflow encourages evaporation, reducing moisture that contributes to the smell. Thirdly, when you’re a few blocks from your destination, reach over and turn off the AC button. It is usually a small button with a snowflake design. This shuts off the air conditioning compressor so the evaporator under the dash is no longer cooling and collecting moisture removed from the air. With the fan still blowing, the evaporator will dry out which can reduce bacterial growth.


We’ve shared 7 situations that can be misdiagnosed as car air conditioning problems and each one costs less to fix than air conditioning system repairs. When your auto repair professional checks these basics first, it can save you an unnecessary and expensive air conditioning system repair.

And if you haven’t had air conditioning service on your vehicle in the past several years, now is a great time to have that done. If you live or work in the Eagle or Boise area, consider contacting AutoTranz Transmissions and auto repair to make sure your AC system is able to do its job. Call us at (208) 722-7429 or request an appointment online.

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