An automotive refrigeration system has four main components: the compressor, condenser, expansion valve, and evaporator. At times, the problem with air conditioning systems will not involve any of the components.
The issue I've encountered most often is low refrigerant pressure. The coolant R134a is the refrigerant used in the vast majority of modern automobiles, and it is inevitable that your system will slowly leak this volatile chemical into the atmosphere over time. This advice is applicable to almost all automobile air conditioning systems, as the refrigeration cycle is a very well known and widely used application in the automotive industry.
- Compressor: This inlet to this unit is the low-pressure side refrigerant line. The outlet of this unit is the high-pressure side refrigerant line. You can tell the difference between the two as the low-pressure sideline has a wider diameter. This unit is operated by the serpentine belt that moves as the engine rotates. The compressor is only working when you have the air conditioning on. An electrical signal from the a/c on/off control in the car will tell the compressor clutch to engage or disengage. As a side note, with the air conditioning in the "off" position, there is less resistance on the engine and fuel economy will be better as compared to air conditioning being on.
- Condenser: The inlet to this unit comes from the high-pressure refrigerant line. The purpose of the condenser is to cool this high-pressure, high-temperature refrigerant vapor to a lower-temperature coolant in a liquid-vapor phase. From here, the flow goes to the expansion valve.
- Expansion valve: Pressure reduction through this unit allows the refrigerant to lose pressure and return to the liquid phase, which will be useful for the next unit.
- Evaporator: The evaporator is simply a heat exchanger that will take full advantage of the thermodynamics of refrigerant evaporation. Warm air passing through this heat exchanger will evaporate the refrigerant. When the refrigerant evaporates from a liquid to a vapor phase, the latent heat of vaporization of R134a is felt by cold air whooshing through your air ducts. The outlet of the evaporator will be the low-pressure refrigerant line feeding your compressor.
Further knowledge of the refrigeration cycle can be learned by taking courses in thermodynamics or by learning from used college textbooks, which are dirt cheap on auction sites. Automotive repair manuals are helpful, as well. They will provide the details of what is going on in your system, where the textbook will present the principles.
Step I: Checking Refrigerant Pressure
- Locate the low-pressure port feeding the compressor.
- Remove the cap on this line.
- Attach your R134an air conditioning refill kit hose to this line by pressing it firmly into place.
- Observe the gauge. If pressure is noted on the gauge, proceed to next step. If no pressure is seen, then your a/c system will need to be evaluated for leaks and have the air evacuated from the system. I'd recommend either taking it into the shop or investing in a manifold pressure gauge, vacuum pump and a lot of patience to address the problems further. There are many online tutorials that explain this further troubleshooting and you may need to invest in additional equipment and/or parts if you plan on doing the fix yourself.
Step II: Adding Coolant to Your System
- Attach the R134a coolant to the hose by screwing it on until the seal breaks. Take care to keep the hose and refrigerant bottle away from the belt and moving parts.
- Start your car and put the A/C on the maximum cooling setting with the blower on "high."
- Empty the R134A can until you are at the correct pressure. If your refrigerant was very low, you may need a bit more than 1 can as a Chrysler Pacifica refrigerant capacity is 24oz for 2007-2008, and 19oz for 2004-2006. Do not put too much refrigerant in the system.
- Run the car for several minutes to stabilize the system, and you are good to go.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
joel on July 06, 2020:
im having trouble with the ac my question is it dont want to take recharge can fill like its to much presure
MelissaRL on July 13, 2017:
I am a rookie at anything car DIY, but this seemed easy enough, however I can't seem to get an exact match on the connection to the low pressure port and the can. I get it to relieve pressure as I can hear it, but when I add refrigerant it blows back off. The connection is not strong, Thoughts?
Chris Wutzke on July 02, 2017:
Thanks for taking the time to take the pictures and show where the low pressure port was on a 2007 Pacifica (which is what i have). I just about gave up when the EZ Chill Auto A/C Recharge coupling didn't fit the high pressure port. I had a couple other problems: (1) The instructions say to keep the bottle upright, but the hose for the product is too short for this. I don't know if I lost excess pressure in the can but it seemed to work. (2) My system when from 15lbs to 45lbs very very quickly. It didn't appear that i put much R-134a product in, so i wonder if the pressure built up in the hose but didn't actually go into my A/C system. But my A/C seemed to blow colder, so I will try it for a while and see if i need to put some more refridgerant in. Thanks again for contributing to the community.
Timothy Patterson on July 19, 2016:
Thank you for this tutorial.
I went 2 years without A/C because I thought it would cost too much to fix.
I purchased a $19.97 can of R134 with gauge and now I have A/C for the first time!