Audi A8 Quattro AC Evaporator Replacement Cost

Anytime the evaporator goes bad, there will be one universal symptom. The air from the vents will be warmer than anticipated. This is because a clogged or leaking evaporator will eventually cease to cool the air due to the inability of decompressed refrigerant to reach the evaporator core. In some vehicles, there may be some type of warning like a blinking A/C switch, or you may just notice the air conditioner doesn't work.

To cool the interior of a vehicle down, the air conditioning system uses a multitude of components, and they all have a function to compress or expand refrigerant, which in turn changes the temperature of the refrigerant. But how does the cold refrigerant make the vehicle cold? The answer is the air conditioner evaporator core, or just 'evaporator'. This part is typically housed underneath the dashboard, and replaces the hot air in the vehicle with cool air, which makes it more of a heat exchange.

Understanding the function of the evaporator coil as a heat exchanger requires a little understanding of phase changes from liquid to gas and the effects of high and low pressure on the physical state of refrigerant. As the air conditioner compresses refrigerant, the high pressure raises the temperature of the refrigerant, but as it reaches the evaporator core, it passes through an expansion valve. The expansion valve could easily be called a depressurizing valve as well, as it rapidly depressurized the refrigerant, causing the temperature to drop dramatically. The refrigerant in its cold, gaseous state passes through the evaporator core, causing the metallic core to become extremely cold. The cold evaporator coil is placed in the path of airflow of the blower motor, which causes the air blowing through the evaporator and into the vehicle to become cold as well.

Vehicles with a bad evaporator core can be driven indefinitely, but the comfort and, depending on the climate, safety of passengers should be considered. In extremely hot climates such as deserts, not having an air conditioner in the vehicle could be considered a risk factor for children and seniors.

Most vehicles will go through their entire service life with the same evaporator core, however there are a few factors to be considered. The evaporator core is metallic, and if there is moisture in the air conditioning system, that moisture can cause corrosion. Likewise, a leaking heater core, which is normally housed adjacent to the evaporator core, can leak coolant on the evaporator core, or there may be a rain-water leak from the exterior of the vehicle which causes corrosion to the evaporator core. Additionally, the rubber seals for the air conditioner lines connecting to the core may cause the core to leak, in which case the technician may recommend replacement, depending on whether the fittings for the evaporator are able to maintain a seal once new o-rings are installed.

The evaporator coil is only one point of failure in the air conditioning system, and any servicing technician must diagnose the air conditioner as a whole. Refrigerant pressure must be checked on the high pressure and low pressure side, which will normally provide an understanding of where the problem may be, and where the technician should investigate further. Keep in mind there are electronic components that must be checked with computerized scanning equipment to verify accuracy and functionality, and mechanical components that must function properly as well. Typically the evaporator coil would be suspected after testing for leaks, especially if there is an evident leak without a visible leak detection dye expulsion. Furthermore, if the technician finds that the high pressure side is too high in pressure, and the low pressure side is too low in pressure, the evaporator, among a few other components, will be suspected of a clog.

Evacuating the air conditioning system is necessary when performing any repair which involves opening a refrigerant passage in the air conditioning system. The caveat to that being if the system has lost pressure due to a prolonged or large leak. Once the system is evacuated, the evaporator coil will need to be accessed through a service port near the passenger foot well, or removal of the dashboard. Once the evaporator core is accessed, it can be removed by disconnecting all mounting hardware securing it to the HVAC central housing, and using specialized disconnect tools to remove the air conditioner lines from the evaporator, and possibly the expansion valve. Replacing the evaporator is a matter of refitting the lines, replacing any components removed to access the evaporator, and recharging the system for testing.

we recommend avoiding the use of any off-the-shelf air conditioning repair additives. These additives are only temporary fixes, if they work at all, and can cause damage to air conditioner refrigerant evacuation machines. Also, never attempt to vent refrigerant into the air as this is harmful to the environment and can cause chemical burns. If the system is overcharged, you will need the refrigerant to be recovered by a trained and certified technician.

Older vehicles were made with ozone-depleting, or non-environmental friendly refrigerants, and releasing any refrigerants into the atmosphere is illegal. Federal law requires contained evacuation and disposal of refrigerants, and this requires fairly expensive machinery. Federal law also states that the older types of refrigerant be replaced with a more environmentally friendly version when the air conditioner service is performed. This will likely require several components and seals to be replaced to ensure compatibility with the new refrigerant. Due to the nature of air conditioning systems, adding refrigerant is not advised without measuring the high pressure and low pressure side of the system simultaneously, as the pressures may not be affected on both sides of the system.

Air conditioner repair is seldom achievable at home, and will require expensive evacuation equipment, a manifold and gauge set, creating a vacuum in the system, and charging the system. Aside from the lack of equipment that most DIYers will face, there is a danger of harm to person, equipment, and the vehicle when repairs or diagnostics are performed incorrectly. When it comes to servicing the air conditioner, it is best left to the pros.