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Old 08-31-2003, 12:48 AM   #1
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Default General A/C Information

I found this on a CHRYSLER site, but a lot of it is good info that I thought I would capture here. I don't agree with not needing gauges, I think they are necessary. As I am going through a few A/C issues of my own over the past week, I found this. I thought it would be good to capture it.


I have been looking into getting the A/C on my car to work and have stumbled across a lot of info and have learned a lot, so I'm going to pass the info on.

First thing is to understand how A/C works…

Compressor failure- Usually this is associated with a clunking noise for awhile and then a smoking belt from the seizure of the compressor. Failure can happen because of two reasons. In most cases it is because oil has leaked from the system over time with refrigerant. The compressor has moving parts and when it becomes starved of oil it seizes resulting in a smoking belt and no more A/C. Also the internals of the compressor are usually spewed throughout the system when this happens. So the whole system must be flushed, receiver drier and the expansion valve must be replaced, and correct amounts of PAG oil be put into the various parts of the system. More on this here

Reason two is failure of the expansion valve. For whatever reason this happens from time to time. The expansion valve meters refrigerant on the high side before the evaporator. It drops the high side pressure from the compressor down to 10-30psi where R-134a is no longer a liquid and becomes a gas in the evaporator. When the expansion valve fails it lets liquid into the compressor which the compressor cannot pump, so it seizes. In some cars the insides of compressor comes apart but this is not a frequent occurrence in the intrepids because the compressor is a pretty durable unit. Usually when the expansion valve fails the belt on the compressor will smoke intermittently. And when the A/C turned off and back on the system continues to work for awhile and does it again…

Evaporator leaks- The A/C system uses PAG oil from the factory. PAG absorbs moisture from the air very very easily. At the factory the system is assembled and moisture gets in it. Apparently dodge did not do a good job with this part and the cars left the factory with high contents of water in the oil. Which the receiver drier is sup post to absorb, but since those things also become filled with moisture easily and aren’t sealed well when packaged they have limited abilities to remove the moisture. So the water in the PAG oil over time mixes with the R-134a and creates acid that eats away at the seals in the system, the evaporator and the condenser resulting in leaks. Moisture also gets in the system when it is not properly serviced and oil with a high content of moisture is put in the system. Oil that comes in plastic bottles often have a high content of moisture as well when new. If oil is added to the system, I suggest getting the oil in a oil charge can, that way you know the oil is dry. Make sure the charge is PAG oil because most oil charges sold in stores are Ester. Ester and PAG oils do not get along well. Anytime the system is opened to repair a leak, the receiver drier must be replaced. It absorbs moisture from the system and becomes quickly filled when exposed to air, it should be the last step when servicing because of this. After that a long vacuum must be pulled to try to get as much moisture out. At least an hour, no less. Many shops skimp on this. If the system is open for a long period of time, you should consider either flushing the system and replacing the oil or converting to hydrocarbon based refrigerant. I have noticed that several members on the board have been using a product called Duracool, which is a mix of propane and butane. The hydrocarbons don’t form acids and actually increase the efficiency and life of the system, and are larger molecules so they as less prone to leaking. Although they are flammable and illegal, the flammability issue is somewhat insignificant because the amount of hydrocarbons to be equivalent to a charge of R-134a is significantly less. The hydrocarbons also have a smell added to them, so you know if it’* leaking. The mix of butane and propane has a lower flash point lower than that of R-134a. There are currently there are 200,000+ vehicles in the USA that are using them with no reported accidents. World wide there are millions. So read up on it anyways though at Another product just like duracool is called Envirosafe. One side note that im looking into is that I heard somewhere that when PAG oil is used with hydrocarbons it cannot be used with R-134a again. So this maybe an issue if you want to sell the car with R-134a installed to avoid legal problems.

Leaks- Common places for leaks on these cars are at the fittings on the compressor and the condenser. The fittings on the compressor on the earlier cars (93 and 94 I think) were very prone to being nicked when assembled, which creates a gap that allows tiny R-134a particles to leak out. The fittings were improved after those years, but if you have ever taken one apart the design isn’t very impressive, and I can see how it can easily leak. To fix this problem the lines must be replaced.

The condenser likes to leak as well. It is the most common place for a leak to be because of the large opens in the front grill of the intrepid. Stones are easily kicked up and into the condenser creating leaks. To prevent this remove the front bumper cover and take some adhesive and some screen from a screen door and place it across the four openings on the back side. I have done this on my car and I feel that it improves the look of the car because the holes no longer look like dead bugs way back on the dirty condenser...all you see is a nice dark mesh. I should note that my car is black.

Servicing- When replacing any component in the system you must either drain the oil from it and replace the same amount of new oil back into the system or go by a service books recommendation for oil replacement for the part. O-rings associated to the part should be replaced as well. Never have the system open for longer than absolutely necessary since the oil absorbs moisture. This means that when you disconnect a part quickly plug opens with something air tight. Preferably you should use the plastic plugs that are sold at automatic stores for this. When the system is put back together the receiver drier should be replaced along with an oz of oil to replace that which is lost when the receiver drier is removed. Do not add oil to the drier itself either. The drier should be the last step with any A/C repair is which the system is opened for any amount of time.

The lines on the A/C system require a special tool to disconnect them. These tools are available at AutoZone in a package of four for $10. If you can’t find them ask at the desk, one of the people there should know what you’re talking about.

When topping off a system- add a few oz’* of oil along with a UV dye to detect leaks. If the A/C needs to be recharged this means the refrigerant is getting out somewhere. A dye should be added so that the leak can be found and accessed to see how much it is leaking. If you don’t do it make sure the shop does it. This way the oil level in the system should remain high. In many cases it is not worth it to fix the leak as this can lead to a very expensive bill and many more problems than just the leak. If you have to recharge the system once a year this isn’t bad, but also isn’t good for the environment.

Flushing- if you need to flush…either buy a kit with solvent or use mineral spirits. Mineral spirits are a cheap alternative. Just take your time and poor it through the part until it comes out clean. After that use compressed air to blow the mineral spirits out. Let the part sit sealed up with a fitting facing down to let the mineral spirits collect at one end. Then remove the seal and blow it out again with compressed air. Repeat this process until no more mineral spirits come out. Fill the part with the proper amount of oil and draw a long deep vacuum to remove the remaining mineral spirits. Do not flush expansion valves, compressors. Or anything else with a restriction in it. You may come across a line with a muffler in it. I don’t know if they use these in our cars, but if you encounter it you cannot flush it and the line must be replaced instead.

Electrical issues- Usually if the charge in the system is fine, then the problem is the pressure transducer. Although the problem can also be the A/C relay, the compressor clutch or in any of the wiring. Start by checking the A/C relay and moving from component to component to find what ones is no longer doing its job. In most cases it is either the pressure transducer, A/C clutch relay, wire to the compressor clutch or the clutch itself. As frustrating as a electrical problem is, it isn’t as bad as having to replace the compressor and flushing the whole system, so it could be worse.

see the old FAQ for more.

System maintenance- The A/C system should be run for about 15minutes a week. Which means wither using to defroster or the a/c it self. For the system to work ambient temperature must be a few degrees above freezing. Although this isn’t critical, it keeps all the seals sealed, and the system ready.

Recharging the system- to recharge you need three things. Refrigerant, a can tap and a thermometer. Preferably you will have a manifold gauge set, but they aren’t 100% necessary. Just back the needle on the can tap all the way back and screw a can of R-134a on. Connect the can to the low side service port and loosen the can a little until you get a spurt of R-134a from your cars A/C system. This purges any air in the can tap and line so you do introduce any air into the system. Next start the car and let it idle and turn the a/c on. The compressor may or may not come on depending on how low the refrigerant charge is. You may need to charge for a while until the compressor comes on. If this is the case, turn the motor off and charge until the can quits getting colder. To charge, turn the pin down on the can tap into the can until it is all the way down. Then back it out and you’ll feel the refrigerant leaving the can. Once the can stops getting cooler, it means the R-134a is no longer evaporating from the can. Once this occurs, there should be enough in the system to engage the compressor. So start the engine and turn on the A/C with the blower on full cool with max fan speed with the windows down. And continue charging until the can again quits getting colder. Swirl it in your hand and see if there is any liquid left in it. If there isn’t the can is empty. Turn the A/C off and back the can tap pin all the way out again. Take the can off and attach another. Again purge the air out and start the a/c again. Continue this until vent temperature become consistent and in the mid 30’* to lower 40 degrees. Never add more than two cans to the system because it is a 28oz system and each can is 12oz. Preferably charge when the ambient temperature is at least 70-80degrees out. Overcharging not only can reduce the performance of the system, but can damage it.

When the system is properly charged, the inlet line to the compressor will be cool to the touch…even sweating if its humid out…the out let will be warm to the touch.

Good luck and keep cool.
Oh and here are some A/C related links. forum with a/c techs… parts, tools and a product called nylog for orings that helps prevent leaks excellent resource. Have parts and will custom make parts for your car. They have many parts that you cannot find anywhere else, and have some good prices as well.

This is by no means 100% correct and I take no responsibility for anything!
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