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Your best source for complete troubleshooting and diagnosis information on auto A/C systems. Our information provides proper repair, recharge, service and maintenance procedures for all automotive air conditioning systems. Regardless if you have a current CCOT (cycling clutch orifice tube) system or an expansion valve and POA valve system, we've got the information you need. From step-by-step help on retrofitting and recharging to complete A/C compressor or component replacement, our A/C manuals provide you a quick and easy methods that have been proven helpful to everybody from the apprentice to the professional.

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Auto A/C Diagnosis, Repair and Recharge details from the leader in auto A/C service and troubleshooting help!

Retrofitting auto A/C Systems
Up until the early 1990’s, all auto A/C Systems used a common refrigerant known as
R-12 (Freon). It was relatively inexpensive and very efficient at transferring heat. However, it was eventually discovered that R-12 (along with all other CFC’s and some other substances) had a very sever negative impact on the earth’s ozone layer. Therefore, R-12 had to be replaced as the preferred refrigerant.

With most industrialized nations signing the Montreal Protocol (1987), the elimination of R-12 was imminent. That created a lot of questions and concerns within the industry. In addition to the concerns about finding a replacement refrigerant, there was the issue of dealing with all the vehicle A/C systems that were on the road already using R-12. This created even more questions and concerns. In order to address all of those existing R-12 systems, it was decided that they should be retrofitted to use another refrigerant. Once again, more questions and concerns.

The purpose of this information is to provide you an objective overview of all the factors that have to be considered when retrofitting your vehicle’s A/C system. You may not be doing the retrofit yourself, but the information will help you understand the potential problems and difficulties that can be encountered. The details will also demonstrate that there really is no such thing as a ‘closed system’ retrofit where you can just add a can and go.

When should you retrofit your A/C System? As a general rule, it’s been decided that for optimum cooling performance, any vehicle A/C system that was designed to work on R-12 should be serviced with R-12 for as long as the supply is available. As we move forward in time and supply shortages appear, it is obvious that pricing will become a major factor in the decision. If you have to retrofit, most aftermarket professionals feel that the best choice of refrigerants is still R-134a, and usually only suggest alternative refrigerants when performance problems are encountered with R-134a.

Some of the factors that have to be addressed when retrofitting the A/C system include:

1) Changes in refrigerant oil
2) A/C System Flush
3) Change of drier or accumulator
4) Caution with condenser design
5) Caution regarding compressor
6) Cooling and/or cooling fan operation
7) Installation of HPCO (High Pressure Cut Out Switch)
8) Installation of charge port adapters
9) System Label

Changes in A/C refrigerant oil: As a rule, R-12 systems use mineral oil and R-134a systems in new vehicles (OE Applications) will use PAG oils. For compatibility issues, the industry moved to use Ester oil (POE) for retrofitting systems. Ester oils were chosen because they were shown to be compatible with both the mineral oil already in the system and the R-134a refrigerant about to be installed. In recent years, new synthetic lubricants have been introduced that have proven work well with all oils. They have shown excellent results, improved cooling performance and have eliminated a lot of the confusion about which oil to use and when.

Flushing the A/C System: This is usually done in order to remove as much of the mineral oil (and any other contaminants) in the system as possible. It also helps to assure against oil overcharging which can reduce cooling performance. When the system is flushed, the proper amount of new oil can be added before recharging. If your are considering retrofitting your a/c system because some other component has failed (ie.: leaking evaporator, compressor failure, etc.) the system should most certainly be thoroughly flushed.

Change of drier or accumulator: The drier or accumulator is the one part that should always be replaced when retrofitting. First of all, it provides filtering for the refrigerant and (most importantly) removes moisture. Doing a retrofit without it would be like changing the engine oil and not changing the filter. Secondly, new replacements will (almost always) be manufactured with either XH-7 or XH-9 desiccant. These are compatible with R-134a while the desiccants used in R-12 systems may not be compatible.

Caution with condenser designs: Although R-134a is an efficient refrigerant, it is not as efficient as R-12. In many older R-12 systems (pre 1980), the original condensers were manufactured in a round tube (usually 3/8” O.D.) and flat fin design. These design configurations usually do not work well with R-134a, and you may have to replace the condenser with a newer design configuration. The replacement condenser should be either an aluminum serpentine design (which incorporates all aluminum vacuum brazed construction) or a parallel flow design that incorporates smaller tube diameters and higher cooling fin density. It would not be wise to purchase the OE replacement condenser for your vehicle as it will probably be the same tube and fin design you already have. Aftermarket suppliers will be your best source.

Caution regarding compressors: In almost all cases, there should be no reason to replace the compressor in order to complete the retrofit, unless it has already failed. The only precaution is for older compressors that will (after retrofitting) be operating at potentially higher pressures. The higher pressures could cause other problems or potentially a complete failure. Other than those precautions, it is good practice to remove the compressor and drain as much residual oil out as possible. (Compressor can not be flushed)

Cooling and/or cooling fan operation: For applications that use belt driven fans, it is important to be sure that fan clutches (if installed) are working properly and that all fan shrouding is in tact. For applications with electric cooling fans, it is important that they be checked so that they are engaging at the proper time to help eliminate excess high pressure conditions. Additionally, a general cooling system inspection is good practice. An overheating radiator can (and will) reduce the ability of the condenser to dispel heat, causing excessive high pressures.

Installation of HPCO (High Pressure Cut Out Switch): This is an excellent safety mechanism that should be installed. The switches are usually designed to perform a few functions. Most importantly, they will stop the compressor from coming on if the system looses it’s charge, and they will also cause the compressor to shut down (temporarily) should the system pressures get too high.

Installation of charge port adapters: Your system should have ‘retrofit adapters’ installed on both the high and low side service ports. They are generally inexpensive and allow R-134a manifold gauge sets to be attached to the system (for charging and testing). They also provide an instant notification to the next service technician that the system has already been retrofitted to R-134a. Be cautious of the fact that many shops will install the adapters for charging purposes and remove them when they are done. This practice is illegal in most jurisdictions and should be frowned upon.

System Label: Each A/C system that has been retrofitted should be labelled, identifying the new refrigerant. Additionally many of the labels allow for the amount of new refrigerant charged. That is helpful because the total amount of R-134a will be different from the total factory specified charge of R-12.

Although this information does not cover every example and possible problem encountered when retrofitting an A/C system, it should provide you a good understanding of all the factors that have to be addressed.

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