Auto Air Conditioning Repair

When your car or truck A/C is not blowing “cold air”, the first thought is to panic. $$$$ signs are going through your mind. Your A/C is broken and the repair is going to be expensive. This article takes the mystery out of automotive air conditioning and serves as a primer so that you can make common repairs yourself and save MONEY on professional repairs.

A/C Principles

There are books and publications that contain volumes of information on the subject of air conditioning repair. This information is often too technical for the you to learn how-to fix your auto air conditioning system lg dryer repair pasadena.

In the nutshell, here is all that you need to know about the fundamentals of refrigeration so that you can fix your auto air conditioning system yourself.

Air conditioning is the process in which air inside the passenger compartment is cooled, dried, and circulated. Heat is removed from inside the vehicle and transferred to the outside air.

All air conditioners whether, it is an auto A/C, household refrigerator or home HVAC, work on the same principles. Namely, a liquid refrigerant is changed to a gas and then back to a liquid. If a change-of-state of the refrigerant is to take place, heat transfer must take place. The two (2) rules that apply to refrigerant are:

1. Refrigerant in a gaseous state collects, absorbs, and holds heat.
2. Refrigerant in a liquid state releases that heat.

A/C Operation and Components

For your auto A/C to blow “cold air”, R-134A refrigerant must pass through and change state in three (3) components, one (1) receiver-dryer, and one (1) expansion valve that makes up the closed auto air conditioning system. The components of the system are:

1. Compressor – A device that pressurizes the heated refrigerant..

2. Condenser – A radiator for refrigerant that transfers the heat that was absorbed in the passenger compartment to the cooler air.

3. Evaporator – Is a small radiator located under dash in the passenger compartment. Liquid refrigerant entering the evaporator creates a pressure loss. The liquid refrigerant absorbs heat from the air blowing across the evaporator. It then boils and changes state to vapor before it enters the suction port of the compressor.

4. Receiver-Dryer – Is a canister that stores the liquid refrigerant when the compressor is not running. It contains a desiccant that removes moisture from the system.

5. Expansion Valve – Is a metering device that controls the amount of refrigerant to the evaporator.

A/C Quick Check

A check that can easily be made to check the health of the A/C system is the “feel check”. With engine running, turn the auto A/C control to “ON” and the blower on “high”. Take a test drive to warm the engine until the A/C system pressures stabilize. Raise the hood. With the A/C “On”, locate the large tubing connected and routed from the compressor (low side) to the expansion valve (inlet side) of the evaporator. Next, locate the small tubing that is connected to the discharge-side of the compressor and routed to the outlet side of the evaporator. When you feel these two (2) lines, you should observe these results:

1. The low-side line should feel “cool” to the touch.
2. The high-side line should feel “warm” to the touch.

If the high-side tubing is not warm and the low-side is not cool, further tests will have to be made as the system is not doing any work. There is an internal problem; such as, a defective component or a leak in your A/C system.

Testing A/C System

Before system temperature tests can be made, a checklist should be followed (below) to setup for testing the A/C system:

1. Set the A/C “ON-OFF” switch to “ON”.
2. Set the temperature control to “maximum cooling”.
3. Set the blower on “high” or the highest number on the control switch.
4. Temperature inside passenger compartment should be stable and getting cooler.
5. Engine speed must be a minimum of 1500 rpm’s.
6. All windows should be be in the “UP” position.

Check Temperature

Your compact car or truck has a small capacity A/C system and a loss of “cooling” would be more noticeable than a larger capacity auto A/C system. If a noticeable loss of “cooling” capacity is noticed, a temperature check at the vent registers should be made. This check can be made with an instant read or digital temperature thermometer.. The discharge air from the vents in the passenger compartment should range from 38 to 42 degrees F.

A/C System Diagnosis

Assuming that the discharge air test measured at the vent registers is out-of-range, a system pressure test will have to be made. Professional A/C technicians connect a tool known as the manifold gauge set to the “low” and “high” side service valves of the system. For you to diagnose and look inside the A/C, it will be necessary to become proficient in the use of the manifold gauge set.

A manifold gauge set that is suitable for the needs can be purchased at most auto supply stores and Internet A/C tool and supply store fronts for less than $50.00. TIP: Look for a gauge set that has a built-in sight glass.

Locate the “low” and “high” side service valves.. Connect the hoses (they are a snap connector fit) to the service valves in the following manner:.

1. Connect the blue hose of the gauge set to the “low-side” service valve of the compressor.
2. Connect the red hose of the gauge set to the “high-side service valve of the compressor.
3. The yellow hose of the gauge set is connected to a vacuum pump or a refrigerant can to add refrigerant to the system. The yellow hose is not connected to the system at this time.

Static Test

If you find an out-of-range temperature reading, the manifold gauge set should be installed on the “low” and “high-side” service valves. With the engine “OFF” and the compressor and clutch not engaged, the blue “low-side” and red “high-side” gauges should show equal readings of approximately 80 to 120psi. These readings would indicate that there is a refrigerant charge in your A/C system. If the readings were 50psi on each gauge, this would indicate that there is refrigerant in the system but a LOW CHARGE. If the readings were 10 to 20psi on each gauge would indicate that there is little or no refrigerant in your A/C system.


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