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My Car AC is Blowing Hot Air – What Do I Do?

on April 3, 2019

My Car AC is Blowing Hot Air – What Do I Do?

on April 3, 2019

With the spring season right around the corner, the weather is going to start warming up, and your car’s interior temperature will rise along with it.  This is especially true for cars left in direct sunlight, as the sun’s energy produces heat that remains trapped within your vehicle.  When this occurs, most drivers rely on their air conditioning to cool down their car’s interior and maintain a comfortable temperature throughout their journey.

However, some drivers may discover that their air conditioning unit is blowing out hot air.   There are several reasons why this may occur, and it is typically due to a hardware malfunction within the vehicle. Depending on the malfunction and the severity of the potential damage, the cost of repair could be quite high.

Common Causes for an A/C Unit to Blow Hot Air

If you’ve ever asked yourself “why is my AC blowing hot air?” it’s likely that your vehicle is experiencing one or more of the following issues:

  • Broken Cooling Fan
  • Broken Condenser
  • Blocked Condenser
  • Low Refrigerant
  • Electrical Faults

Some of these issues can be solved without bringing your vehicle to the mechanic, while others will most likely require assistance from a professional.

Broken Cooling Fan

As its name suggests, the cooling fan is responsible for pulling cool air throughout your car’s radiator.  Your car may utilize one or multiple cooling fans, and they are typically located between the radiator and the engine.  If your car’s cooling fan is malfunctioning, it’s possible that your car will be unable to produce cool air and will only push out hot air through your A/C vents.

Cooling fans rely on electric motors that may go faulty and result in a broken cooling fan.  Your car may begin to overheat as well if your cooling fans are unable to function properly.  A broken cooling fan may lead to more serious malfunctions throughout the vehicle and should always be serviced immediately upon discovery.

Broken or Blocked Condenser

A condenser is one of the most crucial components of any air conditioning unit.  It produces the cold air you expect through the use of refrigerant.  Once filled with the appropriate amount of refrigerant,  the condenser will turn it into a liquid.  That liquid will then travel throughout the condenser’s coils, and eventually, the heat can escape from the unit.

If your condenser is broken, it’s likely that your car’s air conditioning system will not work efficiently.  This is because your condenser is unable to properly guide the hot air running throughout the system; thus, your components will likely overheat.

If your condenser is blocked in any way, the symptoms that you’d experience from a broken condenser would be virtually the same.  Debris or loose parts may block the hot air that the condenser is trying to push out.  This can be fixed by cleaning the condenser or removing whatever is physically blocking the air from exiting the component.

Low Refrigerant

As we explained above, your condenser relies on a substance known as “refrigerant” to work efficiently and condition your air to a cool temperature.  If your refrigerant levels are too low, your condenser will not be able to properly convert it into the liquid used to cool the hot air passing through it.

Low refrigerant typically occurs because there is a leak somewhere within the unit.  Locate the fill port for your car and inspect the area for dirt or any noticeable leaks.  The fill port is located on the left side of the engine bay for most vehicles.  You will find two hoses or pipes next to one another, one larger than the other. 

If your refrigerant is low without any leaks, you may recharge it yourself by performing the following:

1.    Purchase the Required Items

  1. Two 12oz. cans of R-134a refrigerant
  2. One refrigerant dispenser
  3. One pair of goggles

If your vehicle was manufactured before 1994, you would need to purchase R-12 type refrigerant.  However, this guide will not touch on the steps to refill refrigerant on vehicles manufactured before 1994.  All vehicles manufacturered after 1994 typically require R-134a type refrigerant.

Your refrigerant dispenser needs to have both a trigger and a pressure gauge attached to it.  They are required to safely recharge your refrigerant.  You should avoid purchasing a dispenser/refrigerant combination.

2.    Assemble the Dispenser

Equip your goggles and attach the dispenser to the can of refrigerant.  The dispenser has a needle that will automatically puncture the can as you secure it to the top. 

3.    Run the Compressor

You will want to verify that your compressor is running before you attempt to recharge the refrigerant.  You may do so by performing the following:

  1. Start the engine.
  2. Turn the air conditioner on.
  3. Turn the fan to maximum.
  4. Follow the hose from the low side fill port to a cylindrical device attached to the engine (the compressor).
  5. Locate the pulley on the compressor
  6. Determine whether the center part of the pulley is spinning or not.  If it is not spinning, add half of a can of R-134a refrigerant by the upcoming steps in this guide.
  7. Leave the engine running and the air conditioner on maximum until you are finished recharging your vehicle’s refrigerant.

4.    Locate the Low-Pressure Side Refrigerant Fill Port

Your low-pressure side refrigerant fill port will be located underneath a plastic lid with an L printed on the top of it.  Unscrew the cap to reveal the port.

5.    Attach the Dispenser

You should quickly follow these steps to attach the dispenser properly:

  1. Grasp the connecter on the end of the hose.
  2. Lift the outer sleeve of the connector.
  3. Squeeze the trigger for 2 seconds to purge the hose of air.
  4. While still squeezing the trigger and lifting the sleeve, press the connector firmly onto the low-pressure side refrigerant fill port.
  5. Verify that the connector has firmly snapped into place on the fill port.
  6. Release the trigger.
  7. Gently tug on the connector to verify that the connection is secure.

By squeezing the trigger, you can keep refrigerant constantly flowing into the hose.  This will purge it of any air within the hose. This also purges it of any excess moisture within the hose.

6.    Recharge the System

You will need to verify the minimum and maximum acceptable pressure readings for the outside air temperature in which you’re performing the recharge, as it will be your target pressure range.  Some gauges have an adjustable ‘V’ on them to assist you with identifying your target pressure range.  It is crucial that you identify the appropriate target pressure range. If you perform the recharge at a pressure level that exceeds your target, you may cause severe damage to your air conditioning system’s pipes and other components.

Start the Filling Process

  1. Squeeze the trigger for 5-10 seconds while slowly tipping and shaking the can.  You should never turn the can upside down.
  2. Wait 30 seconds for the pressure to equalize.
  3. Read the pressure displayed on the gauge.  You should only measure pressure while the compressor is engaged.  If you find that the pressure is still too low, keep adding refrigerant.
  4. Once you verify that the pressure is correct, stop filling the system and wait a few minutes.
  5. Check the pressure one last time before removing the dispenser hose from the fill port.
  6. Replace the cover on the fill port.

Once the first can is empty, you should turn the can upside down, hold the trigger on the dispenser for 30 – 60 seconds, release the trigger and unscrew the can from the dispenser.  Take your second can and re-screw it to resume recharging your refrigerant. 

Electrical Faults

Electrical malfunctions can be the cause of almost any negative symptoms you’re experiencing with your vehicle.  Many of the components that we enjoy in our vehicle unsurprisingly rely on electrical systems to properly function. 

Your vehicle’s electrical system may have a bad connection or a faulty sensor.  Electrical problems can include a faulty signal from your ventilation system, which can usually be traced back to a broken wire or bad module.  Bad modules will cause sensors to go bad and create false-positive malfunctions in your vehicle’s computer monitoring system. 

If your vehicle’s computer monitoring system detects any anomalies, it will typically instruct the component to shut down to avoid any additional damage to the component.

It’s best to take your vehicle to a mechanic that will be able to properly diagnose your vehicle’s electrical system and translate any diagnostic codes that your vehicle’s computer system is reporting. 

If Your Air Conditioner Is Still Blowing out Hot Air

If you find that hot air is still coming out after both recharging your refrigerant and removing any debris that may be blocking your air conditioning system’s components, you should take your vehicle to a certified mechanic.  While most issues with the air conditioning system can be resolved after a visual inspection, there will be situations when your air conditioning system needs to be repaired by a professional. If you have the best vehicle protection plan, your repairs could be entirely covered!

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