Charge it? (Please don’t!)

For those of us living in the southern California desert, it is impossible to imagine driving a car not equipped with air conditioning. Summer temperatures can easily exceed 110F in this part of the country.

At one time air conditioning was considered an expensive option on cars sold in the US. The early systems were clumsy and often crippled the fuel economy of a standard car because of the added weight of the components along with the power needed to operate the compressor. Newer systems are much lighter and less energy is wasted driving the compressor.

The cost of HVAC (Heating, Ventilation, and Air Conditioning) systems on a modern car can be pretty expensive. Yet most car owners do not have the expensive equipment needed to repair their HVAC systems at home. This is one of the few areas of a car where I discourage anyone unfamiliar with a car to attempt their own repair.

In recent years several automotive parts stores started selling kits to allow car owners to recharge their air conditioning systems at home. I have also seen these same kits sold online as well as large department stores. For about $20 a person can by a can of refrigerant with the tool needed to connect to the low side charging port of the HVAC system. The advertising for these kits show a happy car owner sitting inside their frigid car after recharging the system on their own.

This is one of the worst products I have seen offered to the general public. Not only are they dangerous, the kits offer no fundamental information on how an air conditioning system works. Furthermore, the refrigerant in the kit is often mixed with other chemicals that promise to seal small leaks. Essentially this is introducing a product to the vehicle that was never designed for the car.

A low refrigerant charge will certainly reduce the performance of the HVAC system. If the refrigerant charge is low enough the system will quit working altogether. Yet this isn’t the only thing that will keep an air conditioning system from operating properly. In modern cars there are several electric sensors within the system to help control the compressor’s operation. If one of these sensors fails or receives a negative signal it may shut off the compressor even if the refrigerant charge is sufficient. This is why a professional evaluation of the entire HVAC system is necessary before adding any refrigerant.

Adding refrigerant to a system that is already full can damage the system. Not to mention an overcharged system will also keep the compressor from engaging. Adding refrigerant to a system that is empty can be a waste of money. If the system is empty of refrigerant there is a leak. Recharging the system becomes a waste of money as that recharge will eventually leak out of the system.

Handling refrigerant without the correct equipment can be dangerous. Refrigerant can blind a person if it gets into their eyes. It can also cause freeze burns to the skin almost immediately. The biggest danger however comes when the can is connected to the wrong charging port of the HVAC system. Although this is difficult, it is not impossible. With high side pressures reaching nearly 300psi, a can of refrigerant can burst like a hand grenade.

To correctly charge an HVAC system the refrigerant must me weighed. A professional repair shop will often pull the HVAC system of the car into a vacuum. This will pull any moisture from the system before a charge. Once the vacuum is achieved the mechanic will often make certain the system is able to hold the vacuum. If the system can’t maintain the vacuum, then the system has a leak. Once it is certain the system can hold a vacuum, the mechanic then weighs out the correct amount for the system and begins to charge the system to the correct amount. All of this is performed with a machine that recovers, recycles, and recharges the air conditioning systems on most makes of automobiles. This machine is several thousand dollars and must be inspected and re-calibrated every few years.

While I encourage any owner to take on most repairs they are comfortable with, the HVAC system is one best left to professionals.


Author: yourpocketmechanic

I have been an automobile mechanic for 34 years focusing on the maintenance and repair of cars and trucks. 20 years of my experience comes from working in the retail automotive business. The other 14 years have been spent working with fleet repair for a major utility company.

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