A Guide for Common Car AC Issues

Air conditioning is one of those things that’s easy to take for granted — until you don’t have it. When it’s the middle of summer and the temperature outside is rising, the last thing you want is to be stuck in a car that’s blowing hot air out of the vents … or in a car with an air conditioner that’s not blowing at all.

Being in a car without air conditioning in hot weather isn’t just annoying; it can also be dangerous, since cars heat up quickly. This puts you at risk for dehydration and even heat stroke. It’s even more dangerous for children, the elderly and people with compromised health, so making sure your air conditioning is in good working condition is definitely something you want to make a priority this summer. That means if you’re hitting the road this summer, you’ll probably want to have your mechanic give it a quick checkup before you go.

Visit the Taylor’s Auto Max online scheduling tool to make an appointment to have your vehicle’s air conditioning system inspected before the summer heat begins.

Diagnosing the Problem

Like most things under the hood, air conditioners can stop working for a number of different reasons. Knowing what to look for can help you troubleshoot why your car A/C is not working and let you know what steps you need to take next. Let’s look at the most common reasons your car A/C might have stopped working.

Begin with Testing How your AC Feels

If the air conditioning is set to max cool and fans on high, but is only blowing moderately cool air:

• Check to see that the cooling fans on the condenser or radiator are running when the air conditioning is on.
• Look for any restrictions like leaves, bugs or dirt that would keep air from passing over the condenser.
• Check the cabin air filter to ensure that it is not clogged.

Beyond this, the next step is to always check the pressures in the system using a manifold gauge set. The recommended high-side and low-side pressures can be found in your vehicle’s repair manual, or online. Once you have your gauges hooked up, move on to observing the AC compressor itself.

Refrigerant Leak

This is one of the most common causes of car A/Cs not working. Leaks can originate from a number of different places; it could be the result of rubber seals and hoses breaking down over time, and that allows the refrigerant, Freon, to escape. The bigger danger when this happens goes beyond not having cool air in your car, but those weak spots can also allow moisture to get inside your car’s cooling system and mix with the refrigerant. When moisture and Freon mix together, they create a dangerous acidic combination that can harm you and your passengers, and will corrode your A/C system and cause permanent damage.

As with any type of leak, you want to get this fixed quickly so it doesn’t continue causing problems for your car.

Broken Cooling Fans

Just like you need blowers to push the air conditioning through the vents in your home, your car uses cooling fans to move the refrigerated air into your vehicle’s cabin. When there’s a problem with the fans, you won’t feel any air coming out of the vents.

Cooling fans can stop working properly for a number of different reasons; they might have blown fuses, an electrical short, or could have been cracked by debris from the road. Fortunately, this is fairly simple to fix; your mechanic should be able to replace it quickly and get you back on the road.

A Problem with the Compressor

Your air conditioning relies on a compressor to keep the air moving, but if the compressor isn’t working properly, that refrigerant isn’t going to move around. One of the main reasons a compressor goes bad is from not being used for long periods of time, and the long cool seasons of fall and winter means that many Montanans don’t run their air conditioning for several months.

A compressor can also have problems if the clutch on the compressor gets stuck. If it gets stuck in the “on” position it will make your air conditioning run continuously, and if it’s stuck in the “off” position it will keep the compressor from engaging. You’ll need to have your mechanic look at what is causing the problem with your compressor.

With the engine running, turn the A/C on max cool, set fans high, and make sure that the clutch is engaging on the compressor. Note: this is not the pulley, but the center piece that engages the pulley to the compressor shaft. If the clutch is engaging and disengaging once every few seconds, this is a sign of low refrigerant. You will also see the low-side pressure on your gauge drop rapidly when the clutch engages, hit a point of too-low pressure, then disengage and the pressure will rise. As you add more refrigerant, the gauge will hold steady, with the compressor running, and should hold at the recommended pressure.

If the clutch is not engaging and the system has refrigerant, use a voltmeter to check for voltage getting to the compressor.

If there is voltage – the clutch may be bad.

If there is no voltage – a cycling switch may be bad, a fuse may be blown, and the system may not have enough refrigerant pressure to trip the low pressure cutoff switch that cycles the compressor.

An Issue with the Condenser

The condenser plays an important role; it takes the humid air in the air compressor and depressurizes, cools and liquefies that air. In simpler terms, it helps turn the air cool. When your air conditioning isn’t cooling as much, it could be a sign of a failing condenser.

Electrical Problems

There are several things that can cause electrical problems for your car’s air conditioning. These can include failed switches, a blown fuse, a problem with the control module or something else. Fuses can short out and make the A/C stop working or a loose connection can create an electrical short that is easily fixed.

While electrical issues in the air conditioning system are often easy to fix, they need to be addressed immediately, since they can cause acid buildup. Acid buildup can cause serious damage to your vehicle and can even lead to needing to replace the entire air conditioning system. Staying on top of problems will keep this from happening.

Other Leaks

Leaks are one of the most common problems associated with the air conditioning system.
If pressure is low, then there may be a leak. Using a UV A/C leak detection kit is the easiest way to find a leak. Follow the instructions on the packaging to introduce UV dye to the system and UV light to find the leak.

• Check around all fittings to verify that they are all secure.

• Check hose manifolds on the compressor.

• Check the front seal and the o-rings sealing the pressure switches on the back of some compressors.

• Check where the hoses are crimped onto the fittings.

• Check the Schrader Valves.

• Check for pin holes in the condenser.

• Check where the evaporator drains condensation with UV light. Sometimes oil or dye can be seen.

Note: The dye check will not work if the system is too low and the compressor is not cycling.

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Still not sure? Check these Components

AC Compressor and Clutch

As mentioned before, the AC compressor is a rotating pump that circulates refrigerant (Freon) throughout the system.

Common Problems: Leaks in one or more seals or the compressor itself can occur. Particle contamination from worn parts inside the compressor are a frequent culprit. The engagement clutch, called an AC clutch, can also fail rendering the compressor inoperative.

What to Look For: If the refrigerant is low, check for visible system leaks that appear green and oily. Failing internal components caused by normal wear or low AC Oil levels caused by leaks. Failed AC clutch. Failed power supply to the AC clutch caused by a blown fuse, bad pressure control switch, dash control module or a broken circuit wire. Inspect and test before replacing!

AC Accumulator / Drier

The Accumulator/Drier collects and absorbs moisture. Moisture is like poison to the internal system components and can damage the AC Compressor as well. Depending on your vehicle, you may have an accumulator or a receiver/drier.

Common Problems: Internal failure allowing desiccant material to enter the AC system. Like sugar in the gas tank, this stuff in the wrong places can cause major problems. Leaks can result in over-saturation of the desiccant material that can lead to compressor damage.

AC Orifice Tube / Expansion Valve

The AC orifice tube / expansion device filters and regulates the flow of refrigerant through your air conditioning system. Depending on your vehicle, you may have an orifice tube or an expansion valve.

Common Problems: Contamination is the main cause of failure. If the system pressures are too high and/or too low, the expansion device could possibly be the issue. But first, ensure the refrigerant levels are correct and the radiator/A/C Condenser fan(s) are working properly. Remember, inspect and test before replacing!

AC Evaporator Core

The AC evaporator acts like a huge ice cube with holes in it. It allows the hot, cabin air to flow through the core, rapidly cools this air, and blows it out into the cabin again. The cool air felt from the dash vents is provided by the AC heater blower motor assembly.

Common Problems: The number one cause of failure is a leak due to age and wear. An electronic leak detector is the best way to check for leaks. Give attention to the AC evaporator box water drain tube. Use the tester to search for a leak. A green and oily substance may appear in the drain tube if larger leaks are present.

AC Condenser

The AC condenser looks similar to a radiator and works in conjunction with the radiator fan(s). Air flowing across the AC condenser tubes cool the hot (gaseous) refrigerant that absorbed heat from inside the vehicle. This returns the refrigerant back to a liquid state where it will once again enter the evaporator core and absorb more heat from the interior.

Common Problems: Refrigerant leaks. Contaminant particles from the AC Compressor or AC Accumulator/Drier restricting the flow of refrigerant can lead to poor cooling. While checking the AC Condenser, inspect the Radiator / AC cooling fan motor(s).

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