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THE BASICS OF AIR CONDITIONING

This introduction will discuss the basics of performance air conditioning and factors affecting the selection of the basic components. The seven basic components needed to air condition any car with a conventional system are: compressor, compressor bracket, evaporator (inside car unit), condenser (outside heat exchanger), hoses and fittings, the drier and a safety switch.

Beginning with the compressor, it pumps refrigerant, in gas form, into the high pressure gas discharge line. This gas is loaded with heat it has absorbed from the air flowing over the evaporator coil inside the vehicle. As the heated high pressure gas reaches the condenser, the heat is carried off by the air flowing through the condenser The refrigerant condenses into a liquid which becomes heavier and requires less space. The more efficiently the refrigerant is condensed, the less room it uses in the system. This affects the refrigerant to lower pressures in the high pressure side of the air conditioner. The liquid refrigerant then pours into the receiver/drier where it falls to the bottom of the receiver. A pick-up tube fits into the receiver/drier almost reaching the bottom of the tank. The open end of the tube is always below the liquid level in the receiver/drier, if the system is fully charged. This provides pure liquid to the liquid line (between the drier pick-up tube and the expansion valve). The expansion valve is an orifice that varies in size according to the temperature of the evaporator coil. By changing size, it meters the refrigerant according to the demands of the evaporator When warm, the orifice is largest and gets smaller as the evaporator gets colder. This orifice provides a pressure drop with the resulting drop in refrigerant temperature. The high pressure liquid pours into the larger opening of the evaporator and the low pressure liquid droplets begin to pick up heat which expands the refrigerant to a low pressure (super heated) gas which then returns to the compressor to start the cycle all over again.

Selecting a Condenser

The most difficult problem is getting a condenser large enough, in a place where the air is cool enough, and can be flowed across it well enough to condense the refrigerant adequately. The condenser has to provide a low resistance path for the condensed liquid to flow so pressure build up can be avoided on the existing refrigerant. (Pressure here tends to reduce heat loss which tries to reduce condensation.)

The old vertical vs. horizontal tubes in the condenser comes into play here. Horizontal is best, and a condenser that will fit with the tubes running horizontal is recommended. Why? Because oil flows with the refrigerant in the system and will settle in the lower loops of the condenser, thereby obstructing the flow of liquid. We have seen this single factor increase the internal pressure of the high pressure part of the air conditioner by fifty percent, reducing its ability to work.

A general rule for surface area for an R-12 system is a minimum of 210 square inches on a two row, 5/16inch copper tube and aluminum fin condenser. This is a general rule; it is not absolute. But it is a place to start. HFC-134a requires about 20% more capacity; which means with a conventional tube and fin condenser you need about 20% more size.

Our Super Flow condensers give that increase in capacity without additional size! By using flat tubes manifolded together so that the refrigerant flows through multiple tubes each pass, we get virtually 100% contact of the refrigerant with the condenser tube walls. This design also offers very low restriction in the pathway through the condenser. The Super Flow condenser is an exclusive Vintage Air design which we developed for street rods in 1991. The Super Flow condenser is up to 40% more efficient than a comparable size copper tube and fin type condenser That means we can get more capacity with less space; a good thing for hot rods! A condenser has to have good air flow and must be mounted properly. It must be matched to a compressor of approximately nine (9) cubic inches or slightly less, using a standard aftermarket evaporator. Using this as a standard basic minimum, you can work with the components for desired results. (Example: A three row, 5/16-inch copper tube and aluminum fin condenser could have about 23-percent less surface area. Allow ten percent for loss of efficiency on a thicker core.)

Airflow to the condenser is as important as size. The more the better. Ambient air temperature is more important to an air conditioner condenser than it is to a water cooling radiator because when the refrigerant is exposed to temperatures above approximately 100°F, the chemical expands at a very rapid and disproportionate rate. Water expands more proportionately at much greater temperatures than refrigerant because of a high boiling point. So, we put the condenser in front of the radiator or in the coolest air stream possible to keep the ambient air flowing over the condenser below or as near the century mark as possible. If two condensers are used, the last one in the series should be in the coolest location.

We feel more time and effort should be spent on selecting a condenser than on any other component of your system. The results will be well worth it.

Basic Compressor Facts

The next, most critical part of the air conditioning system in terms of providing trouble free service is matching the compressor to the system.

Why should a compressor be matched to the system? What are the most common types of compressors? How are they different and how can you tell one from another? These are the things we will cover in this part of the outline.

The basic types of compressors commonly used now on street rods are the Sanden, the York/Tecumseh, the General Motors / Frigidaire (DAG and R4), and the Ford Nippondenso.

The Sanden compressor is round with most of its size being its 8 1/2-inches of length, compared to about 5inches in diameter. It is easy to spot with its round shape, aluminum color and over-all size. Its five or seven cylinders run lengthwise and it is an axial compressor. Even though it is commonly known as a rotary, it is not. It is very smooth, with a minimum amount of torque required to operate it because the load is distributed over multiple short stroke cylinders. The compressor has one more characteristics which we like, especially for street rods. That characteristic is its short stroke, low displacement per cylinder configuration which tends to make it less efficient at low RPM ranges (1200 and below), the same speed our engine driven radiator fans are least efficient. This puts less heat load on the condenser and consequently on the radiator at idle speeds. On the average under-condensed street rod, that is a blessing. Above 1200 RPM, efficiency rapidly increases; at operating speeds of 1800 to 2400 RPM it is about the most efficient pump on the market. It can be operated at continuous crank speeds of 6000 RPM. These characteristics make it an almost ideal street rod compressor. Displacement sizes are identified by the numbers on the label on the case. The original number system is interpreted as follows: SD 508= 5 cylinder/8.4 cubic inch, SD 505= 5 cylinder/ 5.6 cubic inch. Sanden has recently developed a new numbering system. The new numbers do not give any information about the compressor like the old numbers did, as an example:

Old number             New number              New HFC-134a number

SD 508                   V9285                         V4509

SD 505                   V5012                         V5071

SD 709                   V7402                         V7819

The Xexel or Diesel Keiki compressor is a clone of the Sanden 508 and the performance bracketry required is comparable.

Briefly, the York compressor, which is becoming a rarity, can be identified by its square shape. Lt is about 8" (L) x 5" (W) x 9" (H) in size, with the clutch. Its displacements given on the front of the compressor in the space marked "P1" or "Part." It will say something like, R209.The"209"tells that it is a two-cylinder compressor with 9-cubic inch displacement. The sizes are as follows: 210 = two-cyl./ 10.3 cu. in., 209 = two-cyl./8.7 cu. in., 206 = two-cyl. /6.11 cu. in.

The York compressor is just like a lawn mower engine, being a two cylinder, reciprocating pump. The reciprocating motion causes it to vibrate more than the Sanden or Frigidaire compressors. It tends to have exceptional low end performance, high pumping peak torque requirements and doesn't like higher RPM's.

The GM/Frigidaire A-6 (long type) compressor shares the same basic design as the Sanden with one cylinder added. It has the same characteristics except that it is very large both in capacity and external dimensions. It is about 12.5 inches long and 5 inches in diameter, with over 12-cubic inches of displacement per revolution. We cover this compressor lightly because in our opinion the only place I would recommend using it would be in an extremely large sedan, with a high capacity evaporator, or two evaporators. A minimum of a 400 sq. in. double row, 5/16-inch copper and aluminum fin condenser would be necessary with HFC-134a, and with a double evaporator the condenser should be at least 600 square inches with HFC-134a, provided air flow and temperature were good. For most street rods that is not necessary or possible. Using the GM/A-6 compressor has been a painful and costly experience for many street rodders.

The GM/Frigidaire R-4 is the short (7 1/2-inch) and fat (7-inch dia.) compressor found on the late GM cars. It has just under 10 cubic inches of displacement per revolution, with four cylinders radiating from its crankshaft. It has basically the same characteristics as the A-6 compressor, except it seems to fit in smaller spaces and is much lighter due to its mostly aluminum construction. The R-4 is larger in capacity than we like in an average street rod, however, it would be a better choice than its bigger brother, the A-6. Rebuilt compressors are not recommended on GM R-4. The GM/Frigidaire DA-6 compressor is slightly larger than a Sanden compressor and will work okay on most street rods. It is an axial compressor with just under 10 cubic inches displacement. Mounting is more difficult on non OEM applications and new replacement costs are high. Rebuilt compressors are not recommended on this model.

The Ford Nippondenso compressor is an axial compressor with about 9.5 cubic inches of displacement. It's fine on applications where OEM equipment is used on your engine. Mounting is more difficult on non OEM applications and new replacement costs are high. We don't recommend rebuilt compressors of this model.

Compressor Capacity is Critical

Capacity is critical in selecting a compressor. Why? The old saying, "a chain is only as strong as its weakest link," comes into play when you select a compressor size or capacity. The weak link in most street rod air conditioning systems is the condenser's ability to handle the demands of the other components. These demands are to condense the refrigerant (R-12) enough to keep the compressor head pressure and corresponding refrigerant temperature within acceptable operating limits (approx. twice the ambient temperature of the day, plus fifteen percent) and to supply the evaporator with adequate refrigerant. Generally speaking, if a compressor has too much capacity the result will be excessive head (internal) pressure and temperature, compressor damage and excessive load on the engine. If a compressor has too little capacity the system will suffer inadequate evaporator performance. Our basic minimum given in the condenser part of this article is larger than most street rods are using; however, we will use that as our standard size condenser. A compressor of 8 or 8.5 cubic inches of displacement per revolution is ideal for a street rod with our standard size condenser, and an average size aftermarket evaporator (approx. 200 cubic inches of coil mass). We would always lean toward a smaller compressor before going to a larger one. Compressor matching makes good sense and will be more critical with use of the new refrigerants.

Safety Switches

Here, we should mention system protection switches. An excessive head-pressure safety switch cuts off the compressor if internal pressure exceeds safe limits and then cuts the compressor back on when the pressure is back down within those limits. A low pressure switch cuts the compressor off when there is excessive refrigerant loss. A binary switch incorporates both of these protections. A trinary switch incorporates both high and low pressure cut offs with an electric fan engagement signal feature. These switches are great insurance on any system, and should always be incorporated.

Compressor Mounting

Another consideration for compressor selection is the way it fits into your available space and how it mounts to the engine. Compressor brackets are available for both the York and Sanden type compressors that will fit in most street rods. The radial compressors are easiest to mount, because of their alternator style mounting.

They do not shake as much, so they require less bracketry as well. Generally, bracket building for air conditioning compressors follows the same principles as any other steel bracket design and fabrication; the simpler the better. There are a few things, however, that are peculiar to this type of bracket. You must have away to adjust the tension of the driving belt. Sliding the compressor, or using an idler pulley mounted on an adjustable eccentric is the simplest way to adjust belt tension. On a driving belt, there is always a tight side and a slack side. We don't like to use an idler pulley because they wear out rapidly and are excess hardware. However, if you do elect to use an idler pulley to adjust belt tension (many times you must), try to put it on the slack run of the driving belt. By doing this you will increase the bearing life of the idler by putting less load on it and reduce belt flop which is always greatest on the slack run of the belt. You should also make sure you have enough belt contacting all pulleys that are driving or driven by that belt. This area is called the "arc of contact."

Universal mounting plates are available for building your own brackets, both York/Tecumseh and Sanden compressors.  

Selecting An Evaporator

We come to the evaporator as the last major component because most all of the aftermarket evaporators will perform their job without problems. The major considerations for selecting are: appearance, size (or fit) and capacity. There are some installation considerations that we will mention in that order. Then we will hit on the highlights of evaporators, as we see them.  

The evaporator is called that because it absorbs heat from the air inside the car which evaporates the refrigerant. The heat is carried off with the refrigerant to be given off to the cool air flowing across the condenser. It takes heat from the recirculating cabin air and gives it off to the outside air.  

Appearance is always a matter of personal preference, with the two different types of evaporators being commonly known as under-dash and in-dash. The under-dash is broken down further as box style or slimline. The slimline is basically a box style unit with a "slim" set of louvers or outlets attached to the front. The slimline is usually longer and adaptable to mast dashes. A box evaporator is just the old under dash evaporator that is made to be functional and inexpensive. An in-dash evaporator is designed to fit behind the dash, with duct hoses carrying air to the louvers, or dash outlets. The tough part here is getting one to fit behind the dash in a street rod.

When component size is reduced, compensation for efficiency is necessary. Blower motors can turn faster and evaporator coils can be fed better, but in most cases when component size is reduced, capacity is also reduced. The in-dash evaporator can be built into any dash shape by selecting the outlet that will fit your vehicle. They can either accent your dash, or be almost invisible.

Installing The Evaporator

When installing the evaporator, it has to be set in the car with the drain pan and tubes down so the condensation will drain. The evaporator (air) outlets should be positioned so they blow on the driver and passengers directly, under or through the dash when possible. Other locations usually produce disappointing results. The outlets should be as close to the evaporator as possible. The thermostat tube should be inserted at least 4 inches into the evaporator coil, and the blower should always recirculate the cabin air. When your refrigerant hoses must go through sheet metal, use either a refrigerant hose grommet or bulkhead fitting. Your drier should always be positioned to produce a "liquid seal" at the pick up tube (this will be vertical for most driers). When your suction line and liquid line run parallel, they can be tied together. The difference in temperature will better help the refrigerant in each line do its job.

An air conditioner has to remove heat faster than is added to the cabin of the vehicle, so it is important to reduce the heat added. Just like reducing weight on a race car so the engine can do more, we reduce heat load in a car by insulating, sealing doors and windows, and tinting the glass. This should be a major step when adding an air conditioning system to any car, and will determine how well the system satisfies your needs.

This information should give you a basic understanding of automotive air conditioning and aid you in selecting the proper components for your particular needs. We encourage you to call us with any questions you may have about air conditioning your street rod, classic car or truck.

Air conditioning your specialty vehicle today requires more knowledge and informed thought than a few years ago. As you may already know, the old industry standard refrigerant known as Freon or R-1 2 is no longer being produced. In fact it hasn't been produced in the U.S. for several years now.

The reason for its demise is based on the fact that the chlorine component (in chloro-fluro carbon 12) has been identified as the primary offender in ozone depletion theory affecting legislation in this country and virtually every other industrialized nation in the world. Production has, as a result, been banned in this country and the end goal is to control its use until it is all but eliminated from common usage.

The refrigerant selected by all automakers worldwide to replace CFC 12 is HFC-134a.The primary difference is the use of hydrogen in place of the chlorine atoms. Hydrogen is relatively benign to the atmosphere and HFC-134a is less harmful. No known atmosphere destruction, no problem!

Still, we would like to go on record as saying all refrigerants, including HFC-134a should be dealt with responsibly, using proper control procedures and recycling machines for each type of refrigerant you handle.

What Does All of This Mean to You?

It means that, as was predicted early on, CFC12 is getting steadily more scarce. If you are currently building a vehicle and hope to have it running soon, you'll need to decide which refrigerant makes the most sense to use. Among the considerations are:

1. Although CFC12is currently available, it is getting harder to find service as shops stop purchasing or replacing the equipment used for CFC-12.

2. The cost of CFC 1 2 in relation to HFC-134a is substantial. It is not uncommon to find CFC12 costing 10 times as much as HFC-134a. This situation will only get worse as supplies dry up.

3.The use of, or even possession of, CFC12 is strictly regulated. Your buddy's stash could result in legal problems!

4. If you install a system designed specifically for CFC-12, or you are restoring one originally designed for CFC-12, you can anticipate a continuing costly and time consuming effort to maintain them.

Performance Of HFC-134a Systems

Although, as is the case with all new technology, there were a few teething problems to be worked out initially, the HFC-134a systems are now fully functional and about as trouble-free as they can get. It has been over nine years since we began our quest to fully develop high quality, high performance air conditioning systems for use with HFC-134a. It has been over eight and half years since the first Vintage Air HFC-134a system was installed in Rick Love's 1939 Ford coupe. We have developed and tested hundreds of such systems in virtually every kind of application and have sold thousands to satisfied customers around the world.

We can say with absolute confidence that these systems, when configured correctly, work as well, or better than current CFC-12 systems.

The Status Of HFC-1 34a Refrigerants And Equipment

As stated above, HFC-134a costs have dropped as production has increased. Now the price per pound is often 10 percent that of CFC-1 2. All automakers currently use HFC-134a in their new vehicles. This has resulted in the widespread availability of, and familiarity with the new refrigerant. This means that your local shop is almost certain to have the right equipment and the knowledge to service these systems.

In addition, most after market air conditioning suppliers not only have available systems designed for use with HFC-134a, but many parts suppliers have retro-fit kits to update many of the older systems.

In short, if you are buying air conditioning components today, you save yourself some money and some grief down the road by purchasing HFC-134a compatible components. Not only is the cost of the new systems comparable to the old CFC-1 2 units, but you will save the high cost of retrofitting that system later with additional components and labor.

If it ain't broke, don't fix it!

Okay, you say, I'm convinced, but I have a CFC-1 2 system in my car now, it works fine. How does all this affect me? Basically, until you have a problem with your CFC-12 system, don't worry about it. As long as it is working properly and is not leaking CFC's into the atmosphere you don't need to do a thing. However, by Federal law, if that CFC-12 system has a leak, you must repair it before it can be recharged. If a professional air conditioning technician is caught charging a leaky system he can be levied a fine that would probably put him out of business!

On the other hand, if you have a CFC-12 air conditioning system that has problems you may want to consider other options. Should you repair it with CFC-12 replacement parts and wait for a future date to "retrofit" the system to HFC-134a? Or should you upgrade and reconfigure the system now for the new refrigerant while you are working on it? The answer depends on the following factors.

Do You Plan To Keep The Car?

If so then you will want to consider updating. At the least, upgrading will allow you to get reasonably priced and timely service while you are on the road. More and more existing service shops are dropping CFC-12 service because of the extra cost, limited number of customers for that service, the cost of additional equipment, and compliance with regulations.

What Kind Of Car Is It?

Some cars typical of  32 through 39's with standard 12"x 22" size condenser in front of the radiator or remote mounted condensers (under the car) may require extra attention. Most will probably require the new manifold style micro tube condensers to increase cooling capacity without an increase in size. This will add a few hundred dollars to the cost of the upgrade. If your car is one that provides plenty of space for a large condenser you probably won't need to change it so the cost of the upgrade is quite reasonable.

What Kind Of Air Conditioning Components Are On The Car Now?

Upgrading requires following the compressor manufacturers guidelines. If you already have a recently manufactured Vintage Air system with a Sanden compressor the upgrade could be very painless.

When did you buy the system?

If you bought the system in the last ten years from Vintage Air, you will have the barrier hose and a Sanden compressor that are HFC capable. (Some earlier systems also included these components, but you need to check with Vintage Air to verify codes and information.) These, along with an HFC-134a capable condenser (again, check with Vintage Air for details), will get you a very inexpensive upgrade.

So you can see that which choice, upgrade or not, depends on several conditions and takes a little careful thought. Based on the excellence performance, wide availability and costs of refrigerant and service, and the vanishing CFC-12 supply, you will almost certainly opt for the HFC-134a system.

What Is Different About The New Systems?

The refrigerant: HFC-134 a is not compatible with the old mineral oil lubricants. You must use an PAG (Poly Alkaline Glycol) oil instead. HFC-134a also has a different pressure/temperature curve so that within the high pressure side of the system there will be more pressure at a given temperature. To keep the pressures down to acceptable levels you must get rid of more heat. In the end this means larger and more efficient condensers.

Condensers

As just stated, the condenser will need to shed more heat. If  there is no more room to increase the physical size of the condenser, a more efficient type of condenser must be used. Be very careful here folks, as there are many people still trying to sell CFC-12 condensers (especially for `32 through `39 street rods) for use with HFC-134a systems. Although claimed to be compatible, it just won't do the job. We designed that condenser some 18 years ago for CFC-12 applications and we can tell you from long experience it just will not work correctly with H FC-134a applications. There are however, many street rods with larger sized condensers that should work fine with HFC-134a. The condenser is very "car-specific," so be sure you get your information from someone with experience and thorough testing to make qualified recommendations to you.

Driers

The drier desiccant (water remover) for HFC-134a is different than that used in CFC-12 systems. It must be replaced. If the new drier is not marked for refrigerant type, don't buy it!

Hose

The hose used with the HFC-134a is different than the older hose. It is called a "barrier hose" for the special barrier preventing water from entering or refrigerant from leaking through the hose material. It also has a nitrite rubber inner tube with a neoprene cover. Vintage Air has been using this hose for over eight years now. Almost all hose currently available is barrier type. Make sure. Call us if you have an older Vintage Air system and are unsure of your hose type.

Fittings

Both the earlier barb-type and the later beadlock fittings will work on HFC-134a. However, proper crimp collars and crimping machine must be used or the hose fittings can be damaged. Many service shops are getting these crimping machines. Never use hydraulic hose collars or crimping machines as these will almost certainly cause a failure. Do not use worm-gear clamps on any of these fittings.

Evaporator

Most evaporators will work fine with HFC-134a after being fitted with an expansion valve calibrated for the new refrigerant. They work well because, regardless of claims to the contrary,

H FC-134a is a more efficient refrigerant, heat transfer is better and exiting air temperature from the H FC-1 3 4a systems is often colder than C FC1 2 systems.

On the other hand, this efficiency can be a problem if you have a pressure-valve controlled system. Such systems include older (1960's) G.M., Ford, and Chrysler OE units. Because the system is controlled by low side pressure and HFC-134a produces lower low-side pressures at a given temperature, these old systems will regulate the refrigerant at CFC-12 levels and above optimal low-side pressures for HFC-134a. Higher vent temperatures result and this may not be acceptable in soma climate and humidity conditions.

Compressor

The compatibility of the compressor varies widely depending on the year of manufacture and make. Vintage Air has always used Sanden compressors. They are a superior product, well proven and adaptable to the HFC-134 a refrigerant. You will want to check with us on date codes to make sure, but most Sanden compressors need only to be drained and refilled with the PAG oil lubricant. In many cases, Vintage Air systems will require the new PAG oil, new drier with the XH-9 desiccant, a couple of new access ports, and verification that the other components are compatible as described above and you are ready to charge with HFC-134a refrigerant.

Vintage Air Invented Performance Air Conditioning

In the tradition maintained over 23 years of operations, Vintage Air will continue to develop leading edge systems for the performance aftermarket. We have pioneered many important advancements in our field and we strive to make climate control for your special vehicle as simple as buying from the right manufacturer. Remember, when you install Vintage Air, you are installing 24 years of knowledge and reliability.

Ordering your new Vintage Air system is easy:

Step One

First, we urge you to take the time to read the "Basics". Air conditioning is not difficult to install but it is a complex system which must be carefully selected and matched to perform to its maximum potential. WE have the knowledge to assist you in finalizing your order. Feel free to call us direct with any technical questions you may have.

Step Two

Based on the specifications for your vehicle you can probably determine which evaporator is best suited to your car. Just note the series number printed directly under the unit photo. Then specify "Heat & Cool" or "Heat, Cool & Defrost" model. (NOTE: The Universal 4-Vent Super Cooler and the Short Pac systems are also available in "Cool Only" model.)

Step Three

Decide which type of standard or optional Proline controls you want.

Step Four

Decide which type of louver package you want. Choose from the standard louvers or upgrade to Proline louvers.

Step Five

Note any additional custom features, optional Proline accessories, and other items such as engine cooling fan, fan shroud, radiator, etc. (Your compressor mounting brackets will be determined by your engine specs).

Step Six

Pick up your phone and start "Living The Cool Life" with your new Vintage Air system!
Call Springfield Street Rod today at 1-800-752-9763  

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