Air Conditioning Information

Here is information to help your decide what components to replace in your air conditioning system. We take it part by part in this breakdown.


If you do not want to replace the current evaporator in your dash you must flush it out with an A/C flush solvent and you must make sure all solvent is removed once done. The reason for this is that the old oil inside your evaporator has absorbed moisture even though you capped it off.


The liquid line needs to be replaced not only due to contaminated oil residue but it also houses the orifice tube. The orifice tube has two functions. It is the restrictor that actually makes the A/C cold. It drops the high pressure side from 190-250 PSI down to the 27-35 PSI on the low. If there is any small amount of clogging this will affect the A/C's performance. The second function is that it is the filter for the A/C system. This captures any debris from the compressor since the compressor is the ONLY moving parts that deals with Freon. For the price of $39.95 it is well worth the preventive maintenance. I also like to replace these just in case the old line has developed a leak from being moved around.


I would replace the discharge line for oil contamination. I also like to replace these just in case the old line has developed a leak from being moved around.


The accumulator simply must be replaced whenever opening the system. It has desiccant inside of that black can. For those of you who do not know what that is you can find it in almost any new pair of shoes. That little bag of white beads. The job of desiccant is to absorb moisture. Once the desiccant absorbs moisture the moisture cannot be extracted from the desiccant. So vacuuming it down will not remove the moisture. If the desiccant is maxed out on the amount of moisture it will affectively absorb then it can no longer absorb moisture from the system while it is operating. Moisture mixed with A/C oil turns to a corrosive acid. Not good!! BTW the desiccant is maxed out after about 30-45 minutes of being open to the atmosphere. The more humid the day the less time you have. I also like to replace these just in case the old line has developed a leak from being moved around.


Condenser is the same as the evaporator. Old moisture contaminated oil needs to be flushed out. I tend to replace it if it is original just because I do not want to lose all of my new Freon in case it has a leak. Condensers have cores like a radiator. If the compressor has had any chunks come out of it these pieces can easily clog the cores and reduce the A/C's ability to cool or make it stop working all together.


The compressor has the same condition as the condenser and evaporator as far as the moisture contaminated oil goes but the compressor has steel internal parts and they will rust. The condenser and evaporator are made from aluminum so no rust issues there. SO let's say you put the old compressor on and it does have some rust. If it works, and it probably will for at least a while, all of the rust and debris that the rust causes get caught in the orifice tube, clog it and now you will need to replace the entire system due to material contamination.

While you are putting it together there are a few rules to follow. Use di-electric grease to lube the o-rings. Any manual will say to use A/C oil, but A/C oil is thin and will dry out causing the o-rings to leak. I have been using di-electric grease on A/C o-rings for almost 20 years and never had one leak.

You must vacuum the system for 30-40 minutes to boil out the moisture. When under a vacuum water boils at room temperature this is why you will see cool steam coming from the vacuum pump.

On a retrofit you must use 8 ounces of Ester oil. I recommend the oil with the green dye. One ounce in the evaporator, 1 in the condenser 2 in the accumulator and 4 in the compressor. IMPORTANT NOTE: before starting motor and A/C, turn compressor clutch by hand 20-30 times to move some of the oil out of compressor and into the line. This prevents hydro lock.

Moisture is CANCER for A/C systems. See this article

Matt Highley, Owner
Fox Mustang Restoration