Tag: car ac evaporator

car ac evaporator

Car A/C Evaporator Core Repair.

The Car A/C Evaporator’s job is to remove heat and humidity from inside the vehicle. Heat and humidity is transferred to the outside of the vehicle by the ac system refrigerant; as warm moist air passes over the aluminum fins of the cool evaporator, heat is transferred from the air to the evaporator. The moisture contained in the air, condenses on the evaporator surface. Dust and pollen passing through the evaporator stick to the wet surface and then drain to the outside of the vehicle. The water can often be seen dripping from the bottom of the vehicle on humid days when the a/c system is operating.

After the expansion valve or orifice tube ,inside the evaporator, the pressure of the refrigerant is allowed to decrease from the high pressure of the liquid refrigerant to a very low pressure. This pressure change inside the evaporator causes the refrigerant to boil, or evaporate. The latent heat of absorption from this state change makes the evaporator cold and allows it to pick up excess heat from the outside air or re-circulated air before it reaches the passenger compartment.

How much does it cost to replace an evaporator coil?

The Car A/C Evaporator core can’t be repaired, it must be replaced. Usually, the evaporator core is not an expensive part, but because is deeply buried underneath the dash is a very hard to reach component and time-consuming repair. In most cases the whole dashboard and center console must be taken apart to get to the hvac box.

The cost for replacing the evaporator core will depend on the make, model, and year of the car. The price range is from about $700.00 to $2000.00 dollars.

What are the symptoms of a bad evaporator core?

Refrigerant Leakage often happens because leaves or other organic material enter the evaporator case through the exterior air intake vents and come in contact with the evaporator’s surface, this moisture surface and decomposition of organic materials, can form corrosive substances which could eventually damage the evaporator core. Moisture inside the system interacts with the oil and refrigerant and creates corrosion inside the evaporator core damaging it from the inside out.   The evaporator fins are also susceptible to clogging from leaves or hair from pets and other outside road debris.


When the Car A/C Evaporator core is leaking, the ac system performance is greatly decreased.

The driver and passengers start to smell some particular odor that is often described as the odor coming from a room that is been locked in a long time.

In cars with dual ac units another sign is that the front unit stops blowing cold air first while the back unit still blows some cool air.

in cars with front ac unit only, the vents from one side of the car blows colder than the other one.

Compressor cycling on and off too often.

What is evaporator core in car AC?

The AC evaporator is one of the heat exchanger in your car. It resembles the condenser but is much smaller and usually more difficult to access it inside the hvac case for repairs. They are generally of the tube and fin design. The evaporator can be thought of as a heat sponge. It creates, together with other ac components in the vehicle a comfortable in cabin air temperature. Typically, when the body is at rest (sitting) and in surroundings of 75 F and 50% humidity with a slight air movement, the body is close to being comfortable.

What is the function of evaporator in air conditioner?

The evaporator works with other components in the A/C system to maintain the pressure and temperature of the evaporator to desired levels. These components can vary, but their main function is the same-they keep the pressure in the evaporator low and keep the evaporator cold without allowing freezing. Some A/C systems use a temperature sensor to prevent evaporator freeze-up by shutting off the compressor.

What is the difference between an evaporator and a condenser?

The evaporator core and the condenser coil both are heat exchangers devices. The main difference between the evaporator core and the condenser is that the evaporator core absorbs heat into the system, cooling down the surrounding air; the condenser on the other side rejects heat created by the compression action of the ac compressor and the heat in the area been cooled.

What state is refrigerant in in the evaporator?

Inside the evaporator core the refrigerant enters as a mixture of about 75% liquid and 25 % vapor. The ideal temperature of the evaporator is approximately 34 F. To maintain this temperature, low pressure liquid refrigerant is metered into the evaporator. As this happens the refrigerant changes state from a liquid to a vapor and cools the evaporator. Warm air is directed over the evaporator from the hvac blower fan, and then the heat in the air is transferred to the refrigerant in the evaporator. This heat is then carried off with the refrigerant to the outside of the vehicle.

Where is located the evaporator core?

The ac evaporator core is located inside the hvac box underneath the dashboard of your car. The temperature of the coil is lower than the in-cabin air temperature being pushed thought it by the action of the blower motor, because of this the evaporator is able to absorb the heat from the passing air and lower its temperature and humidity.

The evaporator absorb heat from the medium being cooled.

Allow the heat to boil off the liquid refrigerant to a vapor in its tubing bundle.

Allow the heat to superheat the refrigerant vapor in its tubing bundle.

Filters the air and get rid of road debris and other forms of contamination from inside the car.

Dehumidify the air and adjust the humidity to level more comfortable to the human body.

What happens to refrigerant in the evaporator?

The refrigerant coming from the metering device enters the evaporator coil from the bottom as a mixture of about 75% liquid and 25 % vapor. Evaporators are usually fed from the bottom to help ensure that no liquid leaves the top without first boiling off to a vapor. If they were fed from the top, liquid could quickly drop by its own weight to the bottom before it is completely boiled off to a vapor. This protects the compressor from any liquid refrigerant.

About halfway up the coil, the mixture becomes more vapor than liquid. The purpose of the evaporator is to boil all of the liquid into a vapor just before the end of the coil. This occurs approximately 90% of the way through the coil, leaving pure vapor.

At the point where the last droplet of liquid vaporizes, we have what is called a saturated vapor. This is the point where the vapor would start to condense if heat were removed from it or become superheated if any heat were added to it.

What are the types of evaporators?

Numerous types of evaporators are available, and each has its purpose. The first evaporators for cooling air were of the natural convection type. They were bare-pipe evaporator with refrigerant circulating through them. The stamped evaporator was one of the first designs to create a large pipe surface.

Types of evaporators

Aluminum parallel-flow ,flat-plate-and-fin evaporator

Forced-draft evaporator

Finned-tube evaporator

Drum-type evaporator

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