If the system uses an orifice tube it will have an accumulator. The accumulator is on the low side of the system at the outlet of the evaporator, and is much larger then a drier. The accumulator is designed to accumulate or store excess refrigerant and to dry the refrigerant. The accumulator contains desiccant to keep moisture out of the system. If liquid passes through the evaporator the accumulator will catch the excess liquid to help avoid damaging the compressor. The filter drier used on expansion valve system are very similar to an accumulator except they do not accumulate refrigerant. The drier is on the high side of the a/c system, and is between the exit side of the condenser and the entrance of the evaporator. The drier has a pipe on the entrance side that opens up to the diameter of the drier. Inside the drier is desiccant that is held in place by two pieces of metal with small holes that allow refrigerant and oil to pass. The desiccant is approximately 1-1/4” thick (approximately 8 ounces) which filters out debris, and dries the moisture out of the system. The liquids pass through the desiccant into the bottom of the drier, where a tube picks up the refrigerant and oil from the bottom and sends it out to the expansion valve. The desiccant in the accumulator and drier are very crucial in eliminating the moisture. This is the reason the drier and accumulator should be changed whenever the system is opened, and the reason an accumulator or drier should always remain capped until the system is ready to be charged.
The final major component of the a/c system is the condenser, which is on the high side of the system. The condenser has become the most crucial part of the system since the industry started using R-134a refrigerant. The condenser’s major function is to condense the refrigerant from a vapor to a liquid. The compressor needs the refrigerant to pass through it as a vapor, the evaporator needs the refrigerant to enter it in a liquid mist form, and the condenser is used to help change the physical form for the system to operate properly. The condenser has to be in a location where airflow can pass through its fins, normally in front of the radiator. The condenser is designed to allow the vapor from the compressor to enter at the top, as the refrigerant flows down to the bottom with air passing the fins the refrigerant can condense into a liquid. If you block airflow of the condenser the a/c system can be affected. If the refrigerant does not convert from a vapor to a liquid it will not enter the evaporator as a liquid which will cause the a/c system to not cool. The condensers used forty years ago for R-12 are not as efficient as the condensers made today but in our facility we still use the old tube and fin style condensers as well as serpentine and achieve a vent temperature of 32-40 degrees out of the vents. For most Jeeps made pre-1996 there is not a new parallel style condenser available so you have to make the original design work with R-134a.
All a/c systems use three types of three types of connections to seal the fittings. Many years ago there were flare fittings. Flare fittings have a cone shaped head on the male side and an inverted cone shape on the female side. The fittings fit together to make a seal where the cones meet. As technology advanced all auto manufactures changed the systems to o-ring style fittings. The o-ring fittings use a small rubber o-ring to make the seal, today most Jeeps use a spring lock, or quick disconnect fitting. This fitting uses two or three o-rings to make the seal but the fittings are not threaded together. There is a male fitting with o-rings on it, and at the end a coupling holding a spring. The female end has a flared end that slides under the spring to lock it into place, there are special tools required to release this connection. All three connections are sealed at the connection of the fitting not the threads, so thread sealer, or Teflon tape are not needed. When a fitting is not sealed at the threads like water fitting in the block thread sealers are not required. It has been said that o-rings used with R-12 will not work with R-134a, after years of research it has been found out that this is not true unless the system is using a gasket that is not black Nitrile or green HNBR.
There are two problems with refrigerants and oils today. The two problems are misleading information and using the products incorrectly. Oil in the a/c systems has changed over the past 40 years. We started with mineral oil for R-12, then the industry made a temporary substitute while the industry starting using R-134a, now all cars are using PAG oil. PAG oil is made in different viscosities for different vehicles. Jeep systems use PAG 46, or Sanden PAG 15. In our facility we have used PAG oil with R-12 and have never seen any adverse affects, so we recommend using PAG in every system. Most Jeep systems require 6-7 ounces of oil if they do not have rear a/c. If you add to much oil the system can overwhelm the refrigerant causing it not change states as necessary for the a/c to work properly. If too much oil is added it can clog the expansion valve and cause the compressor to malfunction.
The refrigerant used in automotive a/c systems has changed over the last 20 years. The reason for this change is because of the harm done to the ozone layer. R-12 refrigerant is a carbon based refrigerant that contained CFC’s which created holes in the ozone layer, the holes increase the sun’s UV rays which can damage our environment. In 1993 the government mandated that every new car use a substitute refrigerant called R-134a. The substitute refrigerant was to be in use for 15 years until a new better alternative was available. During the 15 year period the industry developed many new parts to make auto a/c work very well. Changing oils, and the condenser’s style helped contribute to the cold air you feel inside every new vehicle on the road today. When people tell me R-134a doesn’t get as cold as R-12 I tend to laugh. An a/c system can only get down to 32 degrees Fahrenheit. If the evaporator coil gets any colder than 32 degrees the water that runs off of the coil will freeze. The freezing water will block airflow to the vents, and eventually cause the compressor to starve for oil. As for R-134a being as cold, I have had a/c systems down to 26 degrees out of the vents. It will get as cold, but it may take a few seconds longer to feel at the vents. R-134a condenses at a higher pressure; this is why the condensers were redesigned. The new condensers have a larger surface area for condensing, with the same overall size. When you read about a product that says it will allow the vehicle to get 20 percent colder do not believe the hype. If you get an a/c system that is functioning correctly and blowing 38 degrees out of the vents it is not capable of blowing 20 percent or 7.6 degrees colder. The lower temperature would cause the evaporator to freeze up. The key to making any a/c system blow cold on the hottest days is to make sure it has the nothing blocking the condenser’s air flow, the system has the proper refrigerant charge, and the system has the proper amount of oil in the system. On a final note about the system, we get questions about stop leak. Our advise is do not use it, we have seen stop leak cause thousands of dollars in damage. Stop leak is designed to gel up when it mixes with outside air. When the system is taken apart for a repair the stop leak will gel up in the entire system causing blockage that cannot flushed or cleaned out. It is less expensive to fix the leak rather then trying a quick fix solution.