5 Must-Have Features in a Customized Truck Air Conditioning

The air conditioning system in your car is compromised of a compressor, condenser, expansion valve, receiver/drier and evaporator. Refrigerant (also known as freon) is compressed in the compressor and turns into a gas. In the condenser, this gas is cooled to a liquid state and travels to the expansion valve. As the liquid refrigerant goes through the expansion valve, its rapidly cools in the evaporator. A fan blows over the evaporator and cools the air that blows out of your vents. The receiver/drier separates gas and liquid.

Link to Sino Air Conditioner

To be effective, the automotive air conditioner must control these conditions within the vehicle interior:

• It must cool the air
• It must circulate the air
• It must dehumidify the air

These functions are essential if passenger comfort is to be maintained when the ambient temperature and humidity are high. By performing these functions, the air conditioner maintains the body comfort of the passengers.

To understand how an air conditioning system works, we must first understand the nature of heat. For a simple definition, we may say heat is energy. The meshing of gears, the turning of wheels, cause of friction which results in heat. Heat in either extreme will be uncomfortable. The control of temperature means the control of comfort. Air conditioning is a method of controlling heat.

All substances contain heat. Something feels hot when it is warmer then our body temperature. When something contains less heat that our bodies, it feels cold. Cold is merely the removal of some heat. Science tells us that a measurement called “Absolute Zero” is the point at which all heat is removed from an object (approximately -273 C). Any substance above absolute zero temperature contains some heat.

The average person requires a comfort zone of approximately 70-79 F, with a relative humidity of 45-50%. All objects within this range is comfortable to touch.

HEAT MEASUREMENT: A temperature reading gives us the heat intensity of a substance and not the actual quantity of heat. Heat quantity is measured by kilocalories (KCAL). One KCAL is the amount of heat required to raise the temperature of one kilogram of water 1 C (at sea level.) This quantity measurement is used in air conditioning to describe heat transfer during changes of state.

CASES OF HEAT MOVEMENT: Heat always moves from the hotter objects to the colder one. Whenever there is a transfer difference between 2 objects, the heat energy will be transferred from the warmer object to the cooler until both are stabilized at the same temperature. This is known as the law of heat transfer and is the basis go air conditioning operation.

Commonly referred to as R134a, Tetra Flouroethane is a non-ozone depleting refrigerant HFC 134a chemical. R134a was selected as a replacement refrigerant for R12 because R12 contains chlorine and has a major effect to ozone layer depletion. R134a and water have the same abilities to change the state but R134a can do this more rapidly and at a much lower temperature than water. At any time above -15.34 F, R134a changes state and becomes a vapor absorbing large quantities of heat from inside the vehicle. This is what creates the cooling effect you feel inside the vehicle. R134a is stored in containers under high pressure. If it is released into the atmosphere, it will boil at -15.34 F.

HIGH PRESSURE SIDE: Low pressure R134a vapor entering the compressor is compressed to become high pressure/temperature R134a vapor. This is then circulated along with lubricant oil to the condenser. As the high pressure/temperature vapor travels through the condenser, heat is released to the cooler ambient air passing over the condenser tubes condensing the vapor into a liquid. This high pressure/temperature liquid then travels through the filter drier onto the expansion valve where a small variable orifice provides a restriction against which compressor pushes.

LOW PRESSURE SIDE: Suction from the compressor pulls the high pressure/temperature liquid R134a through small variable orifice of the TX valve and into the low-pressure side of the A/C system. The R134a is now under low pressure/temperature vapor where heat from the cabin being blown over the evaporator coil surface is absorbed into the colder low pressure refrigerant The R134a is then pulled through the evaporator and into the compressor. The A/C cycle begins again as the R134a vapor is compressed and discharged under pressure.

The function of a condenser is to act as a heat exchanger and allow heat to flow from the hot refrigerant to the cooler outside air. R134a entering the condenser will be high pressure, high-temperature vapor. As the R134a vapor travels through the tubes of the condenser, heat is given off to the cooler ambient air; the refrigerant vapor condenses and changes to a liquid state. At this point, a large amount of heat is given off by the R134a. The refrigerant will now be a hot, high-pressure liquid.

Most vehicles with air conditioning require an electric fan to assist airflow, either pushing or pulling the air through the condenser, depending on which side of the condenser the fan is placed. The majority of vehicles using R134a require this additional condenser cooling due to the higher operating pressures of R134a. Also, some vehicles have smaller grills or bumper bar openings. This causes poor airflow conditions by the amount of airflow over the condenser. The condenser fan is operator with a/c engaged in various ways:

• medium pressure switch
• indirect connection to the compressor clutch
• via the electronic control module (ECM)
• signal from the a/c switch activation

The Delphi (Harrison) V5 compressor is a non-cycling variable displacement compressor. The compressor varies displacement to control capacity to meet A/C system demand at all operating conditions. The compressor features a variable angle wobble plate in five (V5) cylinder axial piston design. Displacement is controlled by a bellows actuated control valve located in the rear cylinder head. This control valve senses and responds to the system suction pressure or A/C system demand. Through regulation of compressor crankcase pressure, the wobble plate angle, and therefore compressor displacement is variable. In general, the compressor discharge pressure is much greater than the compressor crankcase. Which is greater than or equal to the compressor suction pressure. At maximum displacement, compressor crankcase pressure is equal to the compressor suction pressure. At reduced or minimum displacement, the compressor crankcase pressure is greater than the suction pressure.

The clutch is designed to connect the rotor pulley to the compressor input shaft when the field coil is energized. The clutch is used to transmit the power from the engine crankshaft to the compressor by means of a drive belt. When the clutch is not engaged the compressor shaft does not rotate and refrigerant does not circulate the rotor pulley free wheels. The field coil is actually an electromagnet, once energized it draws the pressure plate towards it, locking the rotor pulley and the pressure plate together causing the compressor internals to turn, creating pressure and circulating refrigerant.

The condenser function is to act as a heat exchanger and allow heat to flow from the hot refrigerant to the cooler outside air. R134a entering the condenser will be a high-pressure high temperature vapor. As the R134a vapor travels through the tubes of the condenser heat is given off to the cooler ambient air; the refrigerant vapor condenses and changes to a liquid state. At this point a large amount of heat is given off by the R134a. The refrigerant will now be a hot, high pressure liquid.

As shown in the illustration, the TXV controls the refrigerant flow by using a system of opposing pressures which will call:

F1: Temperature sensing capillary tube Sealed tube filled with refrigerant. This refrigerant is also filled above the diaphragm (7). The capillary tube sensing bulb (3) is attached to the evaporator outlet tube surface.

F2: Pressure compensation tube This is a hollow tube connected to the evaporator outlet tube and senses the pressure of the R134a refrigerant leaving the evaporator coil. (Other TX valves may not use this tube as pressure is provided internally within the valve).

F3: Pressure spring This spring (6) is located under the ball valve (5)

An expansion valve is utilized in all Classic Auto Air’s evaporator systems. The only function of the valve is to regulate the amount of refrigerant that is released into the evaporator coil. The valve works on the same principle as a needle and seat in a carburetor. The sensing bulb of the capillary tube is attached to the exit (return) side of the coil. Based on the temperature of the return line, the needled will move in and out of the seat. When the sensing bulb reads a high temperature at the return tube, the needle lets the refrigerant flow through the seat unobstructed. As the return tube becomes colder, the needle returns to the seat thereby restricting the flow of refrigerant.

Water, debris and air have a devastating effect on the expansion valve. A plugged condenser, plugged drier or a damaged hose can also be the culprits. Leaving a drier open to the environment could cause the desiccant bag to tear open releasing the contents of the bag into the refrigerant hose. This hose is connected to the expansion valve. If the condenser fittings are left open, small creatures tend to seek out the security of the condenser.

When installing o-rings on the hose connections, be certain the o-ring is properly sealed. Also check for sharp edges on the seat. We recommend a drop or two of mineral oil on the o-ring and the seat. If installed wrong, or the seat has a sharp burr, the o-ring can be cut. A portion of the o-ring can plug the expansion valve.

HIGH PRESSURE SIDE: Low pressure R134a vapor entering the compressor is compressed to become high pressure/temperature R134a vapor. This is then circulated along with lubricant oil to the condenser. As the high pressure/temperature vapor travels through the condenser, heat is released to the cooler ambient air passing over the condenser tubes condensing the vapor into a liquid. This high pressure/temperature liquid then travels through the filter drier onto the expansion valve where a small variable orifice provides a restriction against which compressor pushes.

For more information, please visit Customized Truck Air Conditioning.

LOW PRESSURE SIDE: Suction from the compressor pulls the high pressure/temperature liquid R134a through small variable orifice of the TX valve and into the low-pressure side of the A/C system. The R134a is now under low pressure/temperature vapor where heat from the cabin being blown over the evaporator coil surface is absorbed into the colder low pressure refrigerant The R134a is then pulled through the evaporator and into the compressor. The A/C cycle begins again as the R134a vapor is compressed and discharged under pressure.

The clutch coil is an electromagnet with a strong magnetic field when current is applied. This magnet field is constant as long as the clutch is applied. When the power is removed the magnetic field collapses and creates high voltage spikes. These spikes are harmful to the ECM and must be prevented. A diode placed across the clutch coil provides a path to ground. This diode is usually taped inside the clutch coil connector.

As hot summer weather approaches, your car’s interior needs lots of cool air to get you and your crew around town comfortably. Too often, we take car air conditioning for granted. But having cold air in hot weather is not just another feature. It’s a necessity.

So what can we do to encourage the health of our rides’ climate control before car AC repair is needed? How can we help our car air conditioner operate better?

To find out, we’ve asked Kelley Blue Book’s in-house service and maintenance expert, Gary Hardesty, an A.S.E. certified master technician. His advice can help us keep cool all year long, especially in summer.

Keep reading to learn about common car air conditioning issues, helpful usage tips, and information about your climate control upkeep.

1. Watch High Engine Temperatures on Steep Grades
2. Keep Ducts Under the Windshield Dry and Clear
3. When Odors are Detected, Act Quickly
4. Read the Air Conditioning Section of Owner’s Manual
5. Add Air Conditioning Checkpoints Maintenance Schedule
6. Change the AC Filter When Needed
7. Open Windows to Flush Our Hot Air
8. Use the Fresh Air Vent When Possible
9. Occasionally Run Defrost Mode
10. Use Coldest Setting

1. Watch High Engine Temperatures on Steep Grades

To many motorists, a summer getaway means heading for the mountains. If you’re traveling in hot weather uphill on a steep grade and your car is loaded with people and gear, keep an eye on the engine temperature. Running the air conditioner amplifies stress on your engine, which can contribute to the engine overheating. If you see the engine temp gauge rising, Hardesty says to turn your heat on full blast for a few minutes to help lower the engine temperature and temporarily lessen the burden on the car’s cooling system.

2. Keep ‘Inducts’ Under the Windshield Dry and Clear

Our expert says that water, dirt, and leaves at the base of the windshield reduce operating efficiency and could contribute to mold in the climate control system. The area where the hood and windshield meet is an optimum collection point for debris like pine needles and windblown leaves. Unfortunately, the air conditioning intake is in that area, making it a bad place for old leaves to decay. Hardesty suggests regularly removing any obstructions that restrict airflow, as well as smaller debris that could enter the air distribution box and plug the water drains.

3. When Odors are Detected, Act Quickly

Strange smells in your car’s air vents can be signs of significant problems, but some odors may just be from the previous owner of your car who was a smoker or who allowed pet odors to accumulate. In these cases, Hardesty says that some orange peels placed on the floor of your car for a few days will help. Other options are to spray an odor neutralizer like Ozium into the vents or change the air conditioning filter (skip ahead to tip No. 6 for more details).

But there are some odors to watch out for that might suggest a more significant issue:

• Musty or Mildew Odor

  A musty smell could mean mold entered and remained undrained in the evaporator inside your cooling system. One such way to deal with this: You can run your heater on high for a little while to dry out the evaporator/heating core.

• Sweet Smell

  A sweet smell can mean an antifreeze leak. A professional mechanic can run a leak test to confirm the issue and present service options.

• Gas Odor

  When you smell gas coming from your AC unit, it could indicate a gas leak, which is hazardous. However, it could also mean your gas cap is not secure or is faulty. Either way, get the issue resolved quickly.

How much does it cost to repair car air conditioning?

The most common issues that can constitute a visit to a service bay are refrigerant leaks, defective cooling fans, condenser/compressor malfunctions, and mildew in the vents. These services can range from $150 to $2,000, depending on the severity of the problem.

4. Read the Air Condition Section of Owner’s Manual

Your owner’s manual is full of recommendations and requirements for operating the vehicle, including its climate control and engine cooling systems. Refer to its guidelines for antifreeze coolant to give proper corrosion protection and help prevent overheating. In case your summer travel plans don’t include a road trip, that book in your glovebox also contains information on maintaining the air conditioning system when the vehicle is unused for extended periods.

5. Add Air Conditioning Checkpoints to Maintenance Schedule

Always follow the manufacturer’s recommended maintenance schedule, which includes checking system performance to determine if car air conditioning recharge is needed. Routine inspection may detect potential problems before they become troublesome. Staying on top of AC maintenance contributes to maintaining your fuel economy while keeping the car’s interior comfortable for you and your passengers. At a minimum, have the system checked at the start of each warm season. The service should include checking the drive belt tension, cleaning the condenser fins, and a performance test.

6. Change the AC Filter When Needed

Changing the cabin air filter is an essential part of car air conditioning maintenance. A typical replacement interval is 30,000 miles, but drivers (or passengers) with airborne allergen sensitivities might get filters more frequently to help prevent dust and pollen from circulating inside the car. Clean cabin filters also allow for stronger airflow and can reduce unpleasant odors. Even car owners with minimal DIY skills can save money and replace the filter by following the instructions in the owner’s manual.

7. Open Windows and Start Driving, Then Turn on Your Air 

Don’t expect the air conditioning to instantly cool the cabin during summer weather when the vehicle interior is blistering hot from sitting in the sun all day. You can give a head-start by opening your car’s windows to flush out hot air when you start the car and turn the blower on high. After a minute or so, close the windows and adjust the AC controls as needed to achieve comfort.

8. Use the Fresh Air Vent When Possible

Choosing between recirculating mode and outside air mode is perplexing to some people. Follow this straightforward advice: Use recirculation when outside conditions (smoke, dust, odors, or high humidity) are present. Otherwise, select outside air. Recirculation mode can make the inside air stuffy, and window fogging may occur. Extended use of this mode is not recommended. Instead, use the outside air mode whenever possible.

9. Occasionally Run in Defrost Mode

According to our expert, the defrost mode in your car does more than take the frost off your windows. It prevents mildew and clears up moisture inside the AC unit. Doing this once a week for 5 to 10 minutes can help you avoid mold, mildew, or other unpleasant odors in your car.

10. Use Coldest Setting and Adjust the Fan

Most experts agree that choosing the lowest temperature for your air conditioner is more efficient for the car’s cooling system and saves fuel. Why? Hardesty says that most cooling systems only cool the cabin by 30 degrees and then stop. If you reach that point, then set the temp higher, you also activate the heater. This dual effort causes stress on the system and uses more fuel. Instead, set the AC fan to low and rotate the vents away from you.

Common AC Issues 

As with many other systems in your car, climate control weakens with wear and tear and leads to car air conditioner repair. Keep an eye out for telltale signs of common and costly issues, such as:

• Refrigerant leaks
• Air conditioner not blowing cold
• Defective cooling fans
• Condenser and compressor malfunctions
• Mildew in the vents

For your car’s heating and air conditioning, service and repair can range from $300 to $2,000, depending on what needs work, so it’s something to watch and maintain. Use the Kelley Blue Book Service Advisor tool to get an estimate for AC repair before making an appointment with your repair shop.

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Editor’s Note: This article has been updated since its original publication. Joni Finkle contributed to this report.

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