A/C Service Overview

Auto AC Repair Diagnostics

Auto Service Experts auto air conditioner diagnostic includes hooking your vehicle up to the latest AC machine and computer scanners. This specialized machine checks high pressure and low pressure readings, and is used to determine if your car air conditioner is low on Freon. If so, it can recover and add Freon to the correct vehicle manufacturer recommended amount.

AC Dye Tests

If the vehicle is too low on Freon and the compressor will not turn on, or if the leak is small and impossible to see with the naked eye, you may require a dye test to determine the source of the leak. A dye test involves injecting fluorescent dye into the car’s air conditioning system and running it until traces of the dye (visible under UV light) can be seen at the location of the leak. The fluorescent dye helps to point out hard to detect leaks because freon is transparent and therefore impossible to notice as it escapes the system. Dye tests are performed as a separate service.

Vacuum Test

Refrigerant and air are sucked from the unit with a vacuum pump which creates a vacuum within the system. It is then monitored with a vacuum gauge for a period of time, possibly overnight to detect small leaks. If the system does not hold the vacuum, this indicates the presence of an AC leak. The amount of vacuum loss is recorded to determine whether there is a minor or major leak.

AC Electrical Diagnostics

A certified HVAC mechanic will check to make sure there is power from the electrical system (or a pulse with a signal) to the compressor. We check all fuses and relays. If there is an electronic problem beyond the fuses and relays, it may be a computer control problem due to loss of signal. Computer control signal loss problems are repaired as a separate service.

Cabin Air Filter Change or A/C System Cleaning

Your car’s air conditioner is not just responsible for keeping you cool, it also filters and conditions the air you breathe while driving or idling in traffic. The AC system can become clogged when debris and contaminants build up over time. If not properly serviced, bacteria, allergens, mildew, and mold grow inside your vehicle air conditioner, which leads to foul smelling air coming from the vents and can even make you and your family sick!

Most modern automobiles come equipped with cabin air filters located either behind the glove box or in the air intake vents in front of the windshield. These filter and clean air as it enters the heating, ventilation, & air conditioning system, known as the HVAC system. They block and trap dust, pollen, pollutants, and other contaminants before it enters the passenger cabin area, therefore, a dirty cabin air filter can result in the air you breathe inside your vehicle being of poorer quality than the outside air. Cabin air filter replacement is usually recommended every 15,000 miles (or every 5th oil change) but may be necessary more often if driving in heavy traffic congestion or a location with a high level of pollution. If your car or truck does not have a cabin air filter, ask about a cleaning service to eliminate bacteria, mold, and unpleasant smells coming from within the system.

When Should You Have Your Car Air Conditioner Serviced?

• Yearly, Before It Gets Hot!
• As Soon As you notice any decline in your auto AC performance, air is not blowing through the vents properly, or air is not cold.
• If you notice a foul odor or musty smelling air coming from the vents.

AC Service Includes:

• Inspect lines and hoses for corrosion and leaks
• Check high and low pressure readings
• Test output air temperature on the coldest possible setting
• Change / clean refrigerant
• Our mechanics are careful to follow environmentally safe refrigerant handling and disposal procedures as outlined in the Environmentally Sustainable Actions Certification Program.

Benefits of Service:

• Stay cool and comfortable regardless of Pittsburgh’s Variable weather!
• Keep the cost of repairs and replacement parts down by keeping up with regular maintenance.
• Protect your lungs from harmful mildew, mold, bacteria, allergens, and pollutants.

Air Conditioning System Operation

Refrigerant / Freon

AC refrigerant is a chemical compound used to absorb and transfer heat in a refrigerant cycle. It is commonly referred to as Freon, which is actually a trademark name. An automotive air conditioner incorporates several components which work together to circulate, compress, cool, and condense refrigerant. Refrigerant is changed from a gas or vapor state into a liquid state, then back into gas in a continuous cycle. R-12 refrigerant was used in most vehicles until it was banned in 1994 and replaced by the more environmentally friendly R-134a refrigerant. Today’s automobile manufacturers (including GM) are beginning to use HFO class refrigerants such as R-1234y & R-744 which offer increased energy efficiency, are more cost-effective, and have less of a harmful effect on the ozone layer, therefore contribute less to global warming.

***An AC recharge should only be performed by a professional technician using specialized equipment which recovers & recycles refrigerant, minimizing environmental damage.


The AC compressor is sometimes referred to as the heart of a car’s air conditioning system because it is responsible for supplying the system with Freon, or the blood. Freon is a liquid refrigerant which is pumped into the compressor in gas form through the suction port. This gas is then pressurized within the discharge port. The compressed Freon is circulated through a series of different sized cylinders and hoses which create alternating vacuum and pressure, and an expansion valve designed to make the gas contract and expand. Some compressors have a rotary/vane design, and others use pistons and rods to connect to the main shaft. Compressors receive power from a drive belt in the engine. Pressure and cabin temperature inside the compressor are moderated by controls, and refrigeration can be turned on or off by an engagement clutch which is electrically controlled.


From the compressor, the gaseous Freon is pumped into the AC condenser. The condenser uses the engine fan’s cold air to reduce the temperature of the gas and turn it back into liquid. This liquid flows through a filter which collects all foreign contaminants, into receiver-driers (Expansion Valve System), or accumulators (Orifice Tube System), where it is stored.

Orifice Tube System / Accumulator

The AC orifice tube system is designed to keep Freon from flooding the evaporator or entering the compressor in liquid form. These systems control the Freon flow from the accumulators to the evaporator. AC accumulators trap moisture within the system, and clean and store refrigerant. The orifice tube changes Freon from high pressure liquid into low pressure liquid and supplies only a mist of Freon to be evaporated back into gas. The orifice tube system is found in most domestic cars, trucks, and SUVs.

Expansion Valve System / Receiver-Drier

Most foreign or import vehicles are equipped with an AC expansion valve system which takes the place of the orifice tube system. The systems use receiver-driers instead of accumulators, which are very similar in operation and function, with the major difference being where they are located within the air conditioning system. A receiver-drier is connected on the high pressure side, and an accumulator is on the low pressure side.


Compressed refrigerant is transferred from the condenser to the AC evaporator. Excess condensation is allowed to escape the evaporator through a drain tube. This condensation can be seen dripping beneath the vehicle and may leave a substantial puddle. This is normal, although it is sometimes mistaken for an AC Leak. From the evaporator, the gaseous freon returns to the suction port of the compressor to repeat the process.

Air Conditioner Components which periodically need Service:

Common Car Air Conditioner Problems often involve repairs or replacements of one or more of the following components:

• Compressor
• Condenser
• Liquid Line
• Orifice Tube
• Receiver/Drier
• Accumulator
• Control Head
• Low Pressure Switch
• Amplifier
• Ambient Temperature Sensor
• Dual Climate Control
• Evaporator
• Cabin Filters
• High-Pressure Switch
• Vintage Air
• Manifold Hoses
• Blend Door Actuators
• Evaporator Cases
• R-12
• 134-A
• Retrofit
• High and Low Fittings
• Blower Motors
• Relay


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